System for collecting light

ABSTRACT

A thin transparent layer can be integrated in a head mounted display device and disposed in front of the eye of a wearer. The thin transparent layer may be configured to output light such that light is directed onto the eye to create reflections therefrom that can be used, for example, for glint based tracking. The thin transparent layer can be configured to reduced obstructions in the field of the view of the user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/821,406 (Attorney Docket No. MLEAP.239PR), entitled“SYSTEM FOR COLLECTING LIGHT,” filed Mar. 20, 2019 and to U.S.Provisional Application No. 62/821,977 (Attorney Docket No.MLEAP.239PR3), entitled “SYSTEM FOR COLLECTING LIGHT,” filed Mar. 21,2019. The entirety of each application referenced in this paragraph isincorporated herein by reference.

BACKGROUND Field

The present disclosure relates to optical devices, including augmentedreality imaging and visualization systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world.

Referring to FIG. 1 , an augmented reality scene 10 is depicted. Theuser of an AR technology sees a real-world park-like setting 20featuring people, trees, buildings in the background, and a concreteplatform 30. The user also perceives that he/she “sees” “virtualcontent” such as a robot statue 40 standing upon the real-world platform30, and a flying cartoon-like avatar character 50 which seems to be apersonification of a bumble bee. These elements 50, 40 are “virtual” inthat they do not exist in the real world. Because the human visualperception system is complex, it is challenging to produce AR technologythat facilitates a comfortable, natural-feeling, rich presentation ofvirtual image elements amongst other virtual or real-world imageryelements.

Systems and methods disclosed herein address various challenges relatedto AR and VR technology.

Polarizing beam splitters may be used in display systems to directpolarized light to light modulators and then to direct this light to aviewer. There is a continuing demand to reduce the sizes of displaysystems generally and, as a result, there is also a demand to reduce thesizes of the constituent parts of the display systems, includingconstituent parts utilizing polarizing beam splitters.

SUMMARY

Various implementations described herein include display systemsconfigured to provide illumination and/or image projection to the eye.Additionally or alternatively, the display systems can image the eyeand/or the environment.

In some embodiments, a head mounted display system is configured toproject light to an eye of a user to display augmented reality imagecontent in a vision field of said user. The head-mounted display systemcan include a frame that is configured to be supported on a head of theuser. The display system can also include an image projector that isconfigured to project images into the user's eye to display imagecontent in the vision field of the user. The display system can includea camera, at least one waveguide, at least one coupling optical elementthat is configured such that light is coupled into said waveguide andguided therein, and at least one out-coupling element. The at least oneout-coupling element can be configured to couple light that is guidedwithin said waveguide out of said waveguide and direct said light tosaid camera. The camera can be disposed in an optical path with respectto said at least one out-coupling optical element to receive at least aportion of the light that is coupled into said waveguide via thecoupling element and guided therein and that is coupled out from saidwaveguide by said out-coupling coupling element such that images may becaptured by said camera.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates an example of wearable display system.

FIG. 3 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes.

FIGS. 5A-5C illustrate relationships between radius of curvature andfocal radius.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked waveguide assembly in whicheach depth plane includes images formed using multiple differentcomponent colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an incoupling optical element.As discuss herein, the stack of waveguide may comprise an eyepiece.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 10 schematically illustrates a cross-sectional side view of anexample imaging system comprising an eyepiece, an image projector, alight source for illuminating the eye, and a camera for capturing animage of the eye.

FIG. 11A schematically illustrates the light source for illuminating theeye and the image projector for injecting images in the eye bothemitting light toward an incoupling optical element on a waveguide ofthe eyepiece.

FIG. 11B schematically illustrates projected light from the light sourceand from the image projector coupled into the waveguide.

FIG. 11C schematically illustrates how incoupled light may propagatethrough a waveguide by total internal reflection.

FIG. 11D schematically illustrates light from the light source and fromthe image projector coupled out of the eyepiece.

FIG. 11E schematically illustrates the waveguide and coupling opticalelement configured to propagate incoupled light at least along a fulldimension (e.g., along the x-direction) of the coupling optical element.Light entering the eye is shown from an extended source (e.g., theimaging light will capture a region of the retina).

FIG. 12A is a cross-sectional view that schematically shows lightreflected from the retina exiting the eye and incident on the eyepiece.

FIG. 12B schematically illustrates the example light coupled into thewaveguide of the eyepiece.

FIG. 12C schematically illustrates collimated incoupled light from theeye propagating through a waveguide toward an imaging device.

FIG. 12D schematically shows incoupled light from the eye propagating tothe one or more outcoupling optical elements.

FIG. 12E schematically illustrates light from the eye coupled out of thewaveguide by the outcoupling optical element and directed to the cameraso that an image of the eye (e.g., the retina) can be captured by thecamera.

FIG. 13A schematically illustrates how the imaging system can imagevarious portions of the eye, for example, of the retina, which canenable the orientation of the eye to be determined and the eye positiontracked.

FIG. 13B illustrates a pattern of sequentially displayed fixationtargets used to cause the eye to be directed in a variety of differentdirections during which the retina is imaged. The resultant imagescorrespond to non-identical portions of the retina. For example, whenthe eye is directed in various directions to view differently locatedfixation targets on the display, images captured by the camera includedifferent portions of the retina. These images can be assembled to forma larger map or composite image of the retina.

FIG. 14A schematically illustrates a cross-sectional view of an imagingsystem comprising an eyepiece and a camera for collecting light from theenvironment forward the eyepiece. Light from the environment is shownreflected off or emitted from one or more physical objects in theenvironment. Collection of light from objects in the environment infront of the eyepiece can enable images of the environment to becaptured.

FIG. 14B schematically illustrates light from the environment beingcoupled by the coupling optical element into a waveguide of theeyepiece.

FIG. 14C schematically illustrates an imaging system for collectinglight from the environment using a powered optical element, such as arefractive optical element (e.g., lens such as a wide field of viewlens), forward the eyepiece.

FIG. 15A schematically illustrates an example imaging system comprisinga polarization selective incoupling optical element for receiving lighta illumination source and coupling the light into a waveguide in aneyepiece. The eyepiece further includes a polarization selective lightcoupling element for coupling light out of the waveguide. A polarizermay be used to polarize the light from the illumination source and ahalf wave retarder may be used to rotate the orientation of the linearlypolarized light so as to be turned into the waveguide by thepolarization selective incoupling optical element.

FIG. 15B schematically illustrates light from the eye (e.g., from theretina illuminated with infrared light from the illumination source)being coupled back into the waveguide and directed to a camera for imagecapture.

FIG. 16 schematically illustrates an imaging system configured forimaging an anterior portion (e.g., cornea) of an eye. The imaging systemcomprises an eyepiece such as described above. The imaging systemfurther includes a positive lens for collimating light collect from theanterior portion of the eye for coupling via an optical coupling elementinto a waveguide and propagation to a camera for image capture. Thesystem further comprises a negative lens to offset the positive powerintroduced by the positive lens and to prevent inversion of images ofthe environment in front of the eyepiece that would otherwise be causedby the positive lens.

FIG. 17 schematically illustrates another example imaging systemconfigured for imaging an anterior portion (e.g., cornea) of an eye. Theimaging system comprises a curved wavelength selective reflector thatcollimates light from the anterior portion of the eye for coupling viaan optical coupling element into a waveguide and propagation to a camerafor image capture. The wavelength selective reflector may operate inreflection for infrared light reflected from the eye and in transmissionfor visible light from the environment in front of the user.

FIG. 18 schematically illustrates an example imaging system that alsoincludes a curved wavelength selective reflector that collimates lightfrom the anterior portion of the eye for coupling via an opticalcoupling element into a waveguide and propagation to a camera for imagecapture. Polarization selectivity may be employed to assist incontrolling the path of the light reflected from the eye. Illuminationof the eye is provided via the waveguide instead of a plurality of lightsource between the waveguide and the eye as shown in FIG. 18 .

FIG. 19 schematically illustrates an imaging system that includes ashutter to assist in a procedure for subtracting out noise.

FIGS. 20A-20E schematically illustrate an alternative procedure forsubtracting out noise using wavelength modulation in conjunction with acurved wavelength selective reflector.

FIG. 21 shows an example eyepiece that can be used to simultaneouslyproject light into a user's eye to provide image content thereto whilereceiving image data of the user's eye or of the environment in front ofthe user.

FIG. 22 illustrates a cross-sectional side view of an example of acholesteric liquid crystal diffraction grating (CLCG) having a pluralityof uniform chiral structures.

FIG. 23 illustrates an example of an imaging system comprising aforward-facing camera configured to images a wearer's eye using acholesteric liquid crystal (CLC) off-axis mirror.

FIG. 24 shows another example eyepiece that can be used tosimultaneously project light into a user's eye to provide image contentthereto while receiving image data of the user's eye or of theenvironment in front of the user. In this example, the coupling opticalelement configured to receive light in from the user's or from theenvironment in front of the user is displaced laterally from the imagecontent out-coupling optical element (e.g., exit pupil expander).

FIG. 25 shows another example eyepiece similar to that shown in FIG. 24wherein the coupling optical element configured to receive light in fromthe user's or from the environment in front of the user is laterallyspaced apart from the image content out-coupling optical element (e.g.,exit pupil expander). In the implementation shown in FIG. 25 , however,a space does not laterally separate the coupling optical element 2111from the out-coupling optical element 2110.

FIG. 26 shows an example eyepiece including first and second couplingoptical elements configured to couple light received from the user's eyeor from the environment into a waveguide to be guided therein as well asfirst and second out-coupling optical elements configured to couplelight guided within the waveguide out of said waveguide to one or morecameras.

FIG. 27 is a cross-section through the waveguide, consolidating opticalelements, and out-coupling optical elements shown in FIG. 26 showing apolarizer in an optical path between one of the out-coupling opticalelements and the camera. The polarizer may be used to remove unwantedglint reflections from the cornea when obtaining images of the retina.

FIGS. 28A and 28B are front and perspective views of a coupling opticalelement for coupling light into the waveguide and an out-couplingoptical element for coupling light out of the waveguide to a camerawherein the coupling optical element has a pinhole coupling area. Theoutcoupling optical element is similarly sized and shaped in thisimplementation.

FIGS. 29A and 29B are front and perspective views of a coupling opticalelement for coupling light into the waveguide and an out-couplingoptical element for coupling light out of the waveguide to a camerawherein the coupling optical element has an arcuate slit-shaped couplingarea. The outcoupling optical element is has a pinhole size couplingarea.

FIGS. 30A and 30B are front and perspective views of a coupling opticalelement for coupling light into the waveguide and an out-couplingoptical element for coupling light out of the waveguide to a camerawherein the coupling optical element has a non-arcuate (e.g. straightrectangular) slit-shaped coupling area. The outcoupling optical elementhas a pinhole size coupling area.

FIG. 31 is a front view of an eyepiece including a coupling opticalelement for coupling light into the waveguide and an out-couplingoptical element for coupling light out of the waveguide to a camerawherein the coupling optical element has a non-arcuate (e.g. straightrectangular) slit-shaped coupling area. The eyepiece further includes animage content incoupling optical element for receiving light from animage projector, a light distribution element for directing light fromthe incoupling optical element to an out-coupling optical element forcoupling light guided within the waveguide to a user for viewing imagecontent.

FIGS. 32A and 32B are front and perspective views a pair of couplingoptical elements for coupling light into the waveguide and a pair ofout-coupling optical element for coupling light out of the waveguide toa camera wherein the coupling optical elements has a non-arcuate (e.g.straight rectangular) slit-shaped coupling area. Such a configurationmay be useful for imaging different portions of the eye such as theretina and the cornea (or glint thereon).

FIG. 33 is a front view of an eyepiece including a pair of couplingoptical elements for coupling light into the waveguide and a pair ofout-coupling optical element for coupling light out of the waveguide toa camera wherein the coupling optical elements has a non-arcuate (e.g.straight rectangular) slit-shaped coupling area. The eyepiece furtherincludes an image content incoupling optical element for receiving lightfrom an image projector, a light distribution element for directinglight from the incoupling optical element to an out-coupling opticalelement for coupling light guided within the waveguide to a user forviewing image content.

FIGS. 34A and 34B are front and perspective views of a pair of couplingoptical elements for coupling light into the waveguide and a pair ofout-coupling optical element for coupling light out of the waveguide toa camera wherein the coupling optical elements has a non-arcuate (e.g.straight rectangular) slit-shaped coupling area. The arrangement isdifferent than that shown in FIGS. 32A and 32B.

FIG. 35 is a front view of an eyepiece including a pair of couplingoptical elements for coupling light into the waveguide and a pair ofout-coupling optical element for coupling light out of the waveguide toa camera similar to that shown in FIGS. 30A and 30B. The eyepiecefurther includes an image content incoupling optical element forreceiving light from an image projector, a light distribution elementfor directing light from the incoupling optical element to anout-coupling optical element for coupling light guided within thewaveguide to a user for viewing image content.

FIGS. 36A and 36B are side views of transparent layers that can beintegrated into an eyepiece to direct light to the eye and used, forexample, for glint based gaze tracking.

FIGS. 37A and 37B are side views showing transparent layers fordirecting light to the user's eye positioned at different locations inan eyepiece.

FIGS. 38A and 38B are front and side views of a transparent layerincluding a plurality of optical fibers therein that can be configuredto direct light towards the eye.

FIG. 39 is a perspective view of transparent layer including a pluralityof optical rods therein that can be configured to direct light towardsthe eye.

FIGS. 40A-40C are side, perspective, and top views of a transparentlayer that includes a pair of tilted surfaces that reflect light guidedthrough the transparent layer towards the eye.

FIGS. 40D-40F are top views of additional designs of transparent layersthat include a plurality of tilted surfaces configured to reflect lightguided through the transparent layer towards the eye.

FIGS. 41A, 41B, 42, 43A, 43B, and 44 schematically illustrate exampleeyepieces.

The drawings are provided to illustrate example embodiments and are notintended to limit the scope of the disclosure. Like reference numeralsrefer to like parts throughout.

DETAILED DESCRIPTION

Reference will now be made to the figures, in which like referencenumerals refer to like parts throughout.

FIG. 2 illustrates an example of wearable display system 60. The displaysystem 60 includes a display 70, and various mechanical and electronicmodules and systems to support the functioning of that display 70. Thedisplay 70 may be coupled to a frame 80, which is wearable by a displaysystem user or viewer 90 and which is configured to position the display70 in front of the eyes of the user 90. The display 70 may be consideredeyewear in some embodiments. In some embodiments, a speaker 100 iscoupled to the frame 80 and configured to be positioned adjacent the earcanal of the user 90 (in some embodiments, another speaker, not shown,may optionally be positioned adjacent the other ear canal of the user toprovide stereo/shapeable sound control). The display system may alsoinclude one or more microphones 110 or other devices to detect sound. Insome embodiments, the microphone is configured to allow the user toprovide inputs or commands to the system 60 (e.g., the selection ofvoice menu commands, natural language questions, etc.), and/or may allowaudio communication with other persons (e.g., with other users ofsimilar display systems. The microphone may further be configured as aperipheral sensor to collect audio data (e.g., sounds from the userand/or environment). In some embodiments, the display system may alsoinclude a peripheral sensor 120 a, which may be separate from the frame80 and attached to the body of the user 90 (e.g., on the head, torso, anextremity, etc. of the user 90). The peripheral sensor 120 a may beconfigured to acquire data characterizing a physiological state of theuser 90 in some embodiments. For example, the sensor 120 a may be anelectrode.

With continued reference to FIG. 2 , the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. The data include data a) captured from sensors (which may be,e.g., operatively coupled to the frame 80 or otherwise attached to theuser 90), such as image capture devices (such as cameras), microphones,inertial measurement units, accelerometers, compasses, GPS units, radiodevices, gyros, and/or other sensors disclosed herein; and/or b)acquired and/or processed using remote processing module 150 and/orremote data repository 160 (including data relating to virtual content),possibly for passage to the display 70 after such processing orretrieval. The local processing and data module 140 may be operativelycoupled by communication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 2 , in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information. In some embodiments,the remote data repository 160 may comprise a digital data storagefacility, which may be available through the internet or othernetworking configuration in a “cloud” resource configuration. In someembodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating augmented reality content, to the local processing and datamodule 140 and/or the remote processing module 150. In some embodiments,all data is stored and all computations are performed in the localprocessing and data module, allowing fully autonomous use from a remotemodule.

With reference now to FIG. 3 , the perception of an image as being“three-dimensional” or “3-D” may be achieved by providing slightlydifferent presentations of the image to each eye of the viewer. FIG. 3illustrates a conventional display system for simulatingthree-dimensional imagery for a user. Two distinct images 190, 200—onefor each eye 210, 220—are outputted to the user. The images 190, 200 arespaced from the eyes 210, 220 by a distance 230 along an optical orz-axis that is parallel to the line of sight of the viewer. The images190, 200 are flat and the eyes 210, 220 may focus on the images byassuming a single accommodated state. Such 3-D display systems rely onthe human visual system to combine the images 190, 200 to provide aperception of depth and/or scale for the combined image.

It will be appreciated, however, that the human visual system is morecomplicated and providing a realistic perception of depth is morechallenging. For example, many viewers of conventional “3-D” displaysystems find such systems to be uncomfortable or may not perceive asense of depth at all. Without being limited by theory, it is believedthat viewers of an object may perceive the object as being“three-dimensional” due to a combination of vergence and accommodation.Vergence movements (i.e., rotation of the eyes so that the pupils movetoward or away from each other to converge the lines of sight of theeyes to fixate upon an object) of the two eyes relative to each otherare closely associated with focusing (or “accommodation”) of the lensesand pupils of the eyes. Under normal conditions, changing the focus ofthe lenses of the eyes, or accommodating the eyes, to change focus fromone object to another object at a different distance will automaticallycause a matching change in vergence to the same distance, under arelationship known as the “accommodation-vergence reflex,” as well aspupil dilation or constriction. Likewise, a change in vergence willtrigger a matching change in accommodation of lens shape and pupil size,under normal conditions. As noted herein, many stereoscopic or “3-D”display systems display a scene using slightly different presentations(and, so, slightly different images) to each eye such that athree-dimensional perspective is perceived by the human visual system.Such systems are uncomfortable for many viewers, however, since they,among other things, simply provide different presentations of a scene,but with the eyes viewing all the image information at a singleaccommodated state, and work against the “accommodation-vergencereflex.” Display systems that provide a better match betweenaccommodation and vergence may form more realistic and comfortablesimulations of three-dimensional imagery.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes. With reference toFIG. 4 , objects at various distances from eyes 210, 220 on the z-axisare accommodated by the eyes 210, 220 so that those objects are infocus. The eyes 210, 220 assume particular accommodated states to bringinto focus objects at different distances along the z-axis.Consequently, a particular accommodated state may be said to beassociated with a particular one of depth planes 240, with has anassociated focal distance, such that objects or parts of objects in aparticular depth plane are in focus when the eye is in the accommodatedstate for that depth plane. In some embodiments, three-dimensionalimagery may be simulated by providing different presentations of animage for each of the eyes 210, 220, and also by providing differentpresentations of the image corresponding to each of the depth planes.While shown as being separate for clarity of illustration, it will beappreciated that the fields of view of the eyes 210, 220 may overlap,for example, as distance along the z-axis increases. In addition, whileshown as flat for ease of illustration, it will be appreciated that thecontours of a depth plane may be curved in physical space, such that allfeatures in a depth plane are in focus with the eye in a particularaccommodated state.

The distance between an object and the eye 210 or 220 may also changethe amount of divergence of light from that object, as viewed by thateye. FIGS. 5A-5C illustrate relationships between distance and thedivergence of light rays. The distance between the object and the eye210 is represented by, in order of decreasing distance, R1, R2, and R3.As shown in FIGS. 5A-5C, the light rays become more divergent asdistance to the object decreases. As distance increases, the light raysbecome more collimated. Stated another way, it may be said that thelight field produced by a point (the object or a part of the object) hasa spherical wavefront curvature, which is a function of how far away thepoint is from the eye of the user. The curvature increases withdecreasing distance between the object and the eye 210. Consequently, atdifferent depth planes, the degree of divergence of light rays is alsodifferent, with the degree of divergence increasing with decreasingdistance between depth planes and the viewer's eye 210. While only asingle eye 210 is illustrated for clarity of illustration in FIGS. 5A-5Cand other figures herein, it will be appreciated that the discussionsregarding eye 210 may be applied to both eyes 210 and 220 of a viewer.

Without being limited by theory, it is believed that the human eyetypically can interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited number of depthplanes. The different presentations may be separately focused by theviewer's eyes, thereby helping to provide the user with depth cues basedon the accommodation of the eye required to bring into focus differentimage features for the scene located on different depth plane and/orbased on observing different image features on different depth planesbeing out of focus.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. In some embodiments, the displaysystem 250 is the system 60 of FIG. 2 , with FIG. 6 schematicallyshowing some parts of that system 60 in greater detail. For example, thewaveguide assembly 260 may be part of the display 70 of FIG. 2 . It willbe appreciated that the display system 250 may be considered a lightfield display in some embodiments. In addition, the waveguide assembly260 may also be referred to as an eyepiece.

With continued reference to FIG. 6 , the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or theplurality of lenses 320, 330, 340, 350 may be configured to send imageinformation to the eye with various levels of wavefront curvature orlight ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, the eachof the input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (e.g. a collimated beam) may be injected into eachwaveguide to output an entire field of cloned collimated beams that aredirected toward the eye 210 at particular angles (and amounts ofdivergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (e.g., three) of the waveguides 270, 280,290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 360, 370, 380, 390,400. It will be appreciated that the image information provided by theimage injection devices 360, 370, 380, 390, 400 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is provided by a light projector system 520, whichcomprises a light module 540, which may include a light emitter, such asa light emitting diode (LED). The light from the light module 540 may bedirected to and modified by a light modulator 530, e.g., a spatial lightmodulator, via a beam splitter 550. The light modulator 530 may beconfigured to change the perceived intensity of the light injected intothe waveguides 270, 280, 290, 300, 310. Examples of spatial lightmodulators include liquid crystal displays (LCD) including a liquidcrystal on silicon (LCOS) displays. It will be appreciated that theimage injection devices 360, 370, 380, 390, 400 are illustratedschematically and, in some embodiments, these image injection devicesmay represent different light paths and locations in a common projectionsystem configured to output light into associated ones of the waveguides270, 280, 290, 300, 310.

In some embodiments, the display system 250 may be a scanning fiberdisplay comprising one or more scanning fibers configured to projectlight in various patterns (e.g., raster scan, spiral scan, Lissajouspatterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 andultimately to the eye 210 of the viewer. In some embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a single scanning fiber or a bundle of scanningfibers configured to inject light into one or a plurality of thewaveguides 270, 280, 290, 300, 310. In some other embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a plurality of scanning fibers or a plurality ofbundles of scanning fibers, each of which are configured to inject lightinto an associated one of the waveguides 270, 280, 290, 300, 310. Itwill be appreciated that one or more optical fibers may be configured totransmit light from the light module 540 to the one or more waveguides270, 280, 290, 300, 310. It will be appreciated that one or moreintervening optical structures may be provided between the scanningfiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310to, e.g., redirect light exiting the scanning fiber into the one or morewaveguides 270, 280, 290, 300, 310.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light source 540, and the lightmodulator 530. In some embodiments, the controller 560 is part of thelocal data processing module 140. The controller 560 includesprogramming (e.g., instructions in a non-transitory medium) thatregulates the timing and provision of image information to thewaveguides 270, 280, 290, 300, 310 according to, e.g., any of thevarious schemes disclosed herein. In some embodiments, the controllermay be a single integral device, or a distributed system connected bywired or wireless communication channels. The controller 560 may be partof the processing modules 140 or 150 (FIG. 2 ) in some embodiments.

With continued reference to FIG. 6 , the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 270, 280, 290, 300, 310 may each include out-coupling opticalelements 570, 580, 590, 600, 610 that are configured to extract lightout of a waveguide by redirecting the light, propagating within eachrespective waveguide, out of the waveguide to output image informationto the eye 210. Extracted light may also be referred to as out-coupledlight and the out-coupling optical elements light may also be referredto light extracting optical elements. An extracted beam of light may beoutputted by the waveguide at locations at which the light propagatingin the waveguide strikes a light extracting optical element. Theout-coupling optical elements 570, 580, 590, 600, 610 may, for example,be gratings, including diffractive optical features, as discussedfurther herein. While illustrated disposed at the bottom major surfacesof the waveguides 270, 280, 290, 300, 310, for ease of description anddrawing clarity, in some embodiments, the out-coupling optical elements570, 580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of thewaveguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the waveguides 270, 280, 290, 300, 310. In some otherembodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithicpiece of material and the out-coupling optical elements 570, 580, 590,600, 610 may be formed on a surface and/or in the interior of that pieceof material.

With continued reference to FIG. 6 , as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (e.g., a negative lens) beforeit can reach the eye 210; such first lens 350 may be configured tocreate a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This canprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6 , the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (e.g., a digital camera,including visible light and infrared light cameras) may be provided tocapture images of the eye 210 and/or tissue around the eye 210 to, e.g.,detect user inputs and/or to monitor the physiological state of theuser. As used herein, a camera may be any image capture device. In someembodiments, the camera assembly 630 may include an image capture deviceand a light source to project light (e.g., infrared light) to the eye,which may then be reflected by the eye and detected by the image capturedevice. In some embodiments, the camera assembly 630 may be attached tothe frame 80 (FIG. 2 ) and may be in electrical communication with theprocessing modules 140 and/or 150, which may process image informationfrom the camera assembly 630. In some embodiments, one camera assembly630 may be utilized for each eye, to separately monitor each eye.

With reference now to FIG. 7 , an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TIR. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (e.g., forming divergent exit beams), depending on thedepth plane associated with the waveguide 270. It will be appreciatedthat substantially parallel exit beams may be indicative of a waveguidewith out-coupling optical elements that out-couple light to form imagesthat appear to be set on a depth plane at a large distance (e.g.,optical infinity) from the eye 210. Other waveguides or other sets ofout-coupling optical elements may output an exit beam pattern that ismore divergent, which would require the eye 210 to accommodate to acloser distance to bring it into focus on the retina and would beinterpreted by the brain as light from a distance closer to the eye 210than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 8 illustrates an example of a stackedwaveguide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a-240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, e.g., only a single waveguide may be provided perdepth plane.

With continued reference to FIG. 8 , in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 540 (FIG. 6 ) may be configured toemit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6 ) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, e.g., in-coupling optical element 700 disposed on amajor surface (e.g., an upper major surface) of waveguide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of waveguide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) ofwaveguide 690. In some embodiments, one or more of the in-couplingoptical elements 700, 710, 720 may be disposed on the bottom majorsurface of the respective waveguide 670, 680, 690 (particularly wherethe one or more in-coupling optical elements are reflective, deflectingoptical elements). As illustrated, the in-coupling optical elements 700,710, 720 may be disposed on the upper major surface of their respectivewaveguide 670, 680, 690 (or the top of the next lower waveguide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective waveguide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective waveguide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respectivewaveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another. In some embodiments, each in-couplingoptical element may be offset such that it receives light without thatlight passing through another in-coupling optical element. For example,each in-coupling optical element 700, 710, 720 may be configured toreceive light from a different image injection device 360, 370, 380,390, and 400 as shown in FIG. 6 , and may be separated (e.g., laterallyspaced apart) from other in-coupling optical elements 700, 710, 720 suchthat it substantially does not receive light from the other ones of thein-coupling optical elements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 730 disposed on a major surface(e.g., a top major surface) of waveguide 670, light distributingelements 740 disposed on a major surface (e.g., a top major surface) ofwaveguide 680, and light distributing elements 750 disposed on a majorsurface (e.g., a top major surface) of waveguide 690. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on a bottom major surface of associated waveguides 670, 680,690, respectively. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on both top and bottom majorsurface of associated waveguides 670, 680, 690, respectively; or thelight distributing elements 730, 740, 750, may be disposed on differentones of the top and bottom major surfaces in different associatedwaveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, e.g.,gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (e.g., TIR between the top and bottom majorsurfaces of each waveguide). In some embodiments, the layers 760 a, 760b are formed of air. While not illustrated, it will be appreciated thatthe top and bottom of the illustrated set 660 of waveguides may includeimmediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6 ).

In some embodiments, the light rays 770, 780, 790 have differentproperties, e.g., different wavelengths or different ranges ofwavelengths, which may correspond to different colors. The in-couplingoptical elements 700, 710, 720 each deflect the incident light such thatthe light propagates through a respective one of the waveguides 670,680, 690 by TIR. In some embodiments, the incoupling optical elements700, 710, 720 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated incoupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7 ). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,e.g., orthogonal to, the axis of the OPEs. For example, each OPE may beconfigured to redirect a portion of the light striking the OPE to an EPEof the same waveguide, while allowing the remaining portion of the lightto continue to propagate down the waveguide. Upon impinging on the OPEagain, another portion of the remaining light is redirected to the EPE,and the remaining portion of that portion continues to propagate furtherdown the waveguide, and so on. Similarly, upon striking the EPE, aportion of the impinging light is directed out of the waveguide towardsthe user, and a remaining portion of that light continues to propagatethrough the waveguide until it strikes the EP again, at which timeanother portion of the impinging light is directed out of the waveguide,and so on. Consequently, a single beam of incoupled light may be“replicated” each time a portion of that light is redirected by an OPEor EPE, thereby forming a field of cloned beams of light, as shown inFIG. 6 . In some embodiments, the OPE and/or EPE may be configured tomodify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (e.g.,OPE's) 730, 740, 750; and out-coupling optical elements (e.g., EP's)800, 810, 820 for each component color. The waveguides 670, 680, 690 maybe stacked with an air gap/cladding layer between each one. Thein-coupling optical elements 700, 710, 720 redirect or deflect incidentlight (with different in-coupling optical elements receiving light ofdifferent wavelengths) into its waveguide. The light then propagates atan angle which will result in TIR within the respective waveguide 670,680, 690. In the example shown, light ray 770 (e.g., blue light) isdeflected by the first in-coupling optical element 700, and thencontinues to bounce down the waveguide, interacting with the lightdistributing element (e.g., OPE's) 730 and then the out-coupling opticalelement (e.g., EPs) 800, in a manner described earlier. The light rays780 and 790 (e.g., green and red light, respectively) will pass throughthe waveguide 670, with light ray 780 impinging on and being deflectedby in-coupling optical element 710. The light ray 780 then bounces downthe waveguide 680 via TIR, proceeding on to its light distributingelement (e.g., OPEs) 740 and then the out-coupling optical element(e.g., EP's) 810. Finally, light ray 790 (e.g., red light) passesthrough the waveguide 690 to impinge on the light in-coupling opticalelements 720 of the waveguide 690. The light in-coupling opticalelements 720 deflect the light ray 790 such that the light raypropagates to light distributing element (e.g., OPEs) 750 by TIR, andthen to the out-coupling optical element (e.g., EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. As illustrated, the waveguides670, 680, 690, along with each waveguide's associated light distributingelement 730, 740, 750 and associated out-coupling optical element 800,810, 820, may be vertically aligned. However, as discussed herein, thein-coupling optical elements 700, 710, 720 are not vertically aligned;rather, the in-coupling optical elements are preferably non-overlapping(e.g., laterally spaced apart as seen in the top-down view). Asdiscussed further herein, this nonoverlapping spatial arrangementfacilitates the injection of light from different resources intodifferent waveguides on a one-to-one basis, thereby allowing a specificlight source to be uniquely coupled to a specific waveguide. In someembodiments, arrangements including nonoverlapping spatially-separatedin-coupling optical elements may be referred to as a shifted pupilsystem, and the in-coupling optical elements within these arrangementsmay correspond to sub pupils.

Eye Imaging and Environment Imaging

As discussed above, head mounted displays can be used to provide imagecontent to a user integrated with, in conjunction with, and/orsuperimposed over the view of the world in front of the wearer. Suchhead mounted display systems can be configured to project light into aneye of a user to form augmented reality image content as well as totransmit light from an environment in front of the user to the user. Ahead mounted display system may include one or more cameras for imagingthe environment and/or the user's eye. Outward facing cameras may beused for directly imaging the environment, for example, to determinewhere to place augmented reality image content with respect to objectsin the environment. For example, imaging the environment may provide thelocation of a table such that the head mounted display may render animage of person standing next to the table instead of on the table or inthe table. Inward-facing cameras may be used for directly imaging theeye such as for eye tracking. Disclosed herein are examples ofhead-mounted display systems and/or imaging systems that can beconfigured also to image the eye and/or the environment. In somedesigns, the systems do not require inward and/or outward facing camerasto directly image the eye and/or environment, respectively. Such systemsmay employ one or more cameras that are configured to receive light fromthe eye/environment via the eyepiece such as one or more waveguides inthe eyepiece that are in optical communication with the one or morecameras. With the light collected by the waveguide(s), the one or morecameras can generate images of the eye and/or the environment in frontof the user. Using the waveguide to collect the light for imaging theeye and/or environment may potentially reduce the form factor of thehead mounted display, making the head mounted display possibly morecompact and/or aesthetically desirable.

FIG. 10 illustrates an example imaging system 900 configured to imagethe eye that is integrated with an eyepiece 950 that can be used on inhead mounted display. The eyepiece 950, which can be disposed in frontof the user's eye 210 can be used to both inject image content into theeye as well as image the eye. FIG. 10 shows one eyepiece 950 in front ofone eye 210. Various head mounted display systems such as shown in FIG.2 , may include a pair of eyepieces 950 and associated componentsdisposed in front of respective left and right eyes 210. A singlewaveguide 940 is shown in FIG. 10 , but the waveguide 940 may includeone, two, three, four, six, seven, eight, or more waveguides (e.g., oneor more stacks of waveguides).

The imaging system 900 can include a light source or illumination source960 illuminating the eye to facilitate image capture, the eyepiece 950comprising a waveguide 940 configured to propagate light therein, and/oran imaging device 920 such as a camera for image capture. An imageprojector 930 for producing an image that can be injected into the eyevia the eyepiece 950 is also shown. The eyepiece 950 may include one ormore waveguides 940 configured to transport light from the illuminationsource 960 and/or image projector 930 to the eye and to transport lightfrom the eye to the camera 920. The eyepiece 950 may further compriseone or more coupling optical elements 944 for coupling light out of thewaveguide 940 and to the eye for illuminating the eye and for imageinjection and/or from the eye and into the waveguide for image capture.The eyepiece 950 may additionally comprise one or more incouplingoptical elements 942 for coupling light from the illumination source 960and/or image projector 930 into the waveguides 940 as well as one ormore outcoupling optical elements 952 for coupling light from thewaveguide out to the camera 920.

The eyepiece 950 may be disposed on a frame wearable on the head. Theeyepiece 950 may be disposed in front of the eye 210. The eyepiece 950may have a medial or nasal side closer to the nose of the wearer and anopposite lateral or temporal side closer to the temples and farther fromthe nose of the wearer. In FIG. 10 , the coupling optical element 944 ismedial or nasal with respect to the incoupling 942 and outcoupling 952optical elements (which are lateral or temporal to the coupling opticalelements 944). The illumination source 960 is also more medial or nasalwith respect to the image projector 930 (or the image projector is morelateral or temporal than the illumination source.) The relativepositions can be different, however. For example, the illuminationsource 960 may be more lateral or temporal than the image projector 930in some designs.

The waveguide 940 may comprise a sheet or layer having two majorsurfaces (a forward and a rearward surface), having the largest surfaceareas, disposed opposite one another. The forward surface may be fartherfrom the user's eye 210 (closer to the environment in front of thewearer) and the rearward closer to the user's eye (and farther from theenvironment in front of the wearer) when the user wears the head mounteddisplay. The waveguide 940 may comprise a transparent material with anindex of refraction greater than 1.0 (e.g., glass, plastic) such thatlight may be guided therein by total internal reflection between themajor surfaces. Elements with the same numbers may have the samefunctionality for one or more of the embodiments described herein.

A coupling optical element 944 for coupling light to the eye 210 fromwaveguide 940 and/or from the waveguide to the eye may be disposed on orin the waveguide 940. As shown in FIG. 10 , the coupling optical element944 may be disposed in an optical path between the user's eye 210 andthe waveguide 940 such that light coupled from the waveguide 940 via thecoupling optical element 944 may be incident on the user's eye 210 (forexample to illuminate the eye and/or for image injection). The couplingoptical element 944 may comprise a plurality of turning featuresconfigured to turn light guided within the waveguide out of thewaveguide or turn light incident on the coupling optical element 944 atan angle into the waveguide to be guided therein by total internalreflection. The coupling optical element 944 and turning features may bein physical engagement with the waveguide 940. For example, the couplingoptical element 944 may comprise a holographic or diffractive opticalelement (e.g., surface relief grating) patterned (e.g., etched) in or onthe waveguide 940. The coupling optical element 944 may comprise a layerdisposed on the waveguide 940 or may be formed in the waveguide 940. Forexample, a volume holographic or other diffractive optical element maybe formed by changing the index of refraction of material comprising thewaveguide or a layer disposed thereon. Accordingly, the coupling opticalelement 944 may be disposed in the volume of the waveguide 940 or as alayer disposed thereon.

Depending on the design, the coupling optical element 944 may betransmissive or reflective and may operate in transmission orreflection. For example, the coupling optical element 944 may include atransmissive or reflective diffractive optical element (e.g., grating)or holographical optical element that operates in transmission orreflection respectively, e.g., turning light via that is transmittedtherethrough or that is reflected therefrom. The coupling opticalelement 944 can include a polarization optical element, such as apolarization selective turning element (e.g., polarizer). Thepolarization selective turning element may include one or morepolarization gratings, diffractive optical elements, and/or holographicoptical elements and may comprise liquid crystal structures such asliquid crystal polarization gratings. The coupling optical element 944may be configured to direct light from the image projector 930 and/orlight source 960 guided within the waveguide 940 by total internalreflection (TIR) to the user's eye 210 at an angle less than (e.g., morenormal) than the critical angle so as to be ejected out of the waveguideto the eye. Additionally or in the alternative, the coupling opticalelement 944 may be configured to couple light from the eye 210 into thewaveguide 940 at an angle greater (e.g., less normal) than the criticalangle so as to be guided therein by total internal reflection to thecamera 920.

As shown in FIG. 10 , an incoupling optical element 942 for couplinglight from the illumination source 960 and/or the image projector 930into the waveguide 940 may be disposed on or in the waveguide 940. Theincoupling optical element 942 may be disposed in an optical pathbetween the light source 960 and the waveguide 940 such that lightcoupled from the light source 960 via the incoupling optical element 942is guided within the waveguide 940. The incoupling optical element 942may comprise, for example, a plurality of turning features configured toturn light incident thereon at an angle into the waveguide to be guidedtherein by total internal reflection. The incoupling optical element 942may comprise liquid crystal structures such as liquid crystalpolarization gratings. Additionally or alternatively, the incouplingoptical element 942 may include a blazed grating. The incoupling opticalelement 942 may comprise a layer disposed on the waveguide 940 or may beformed on or in the waveguide 940 (e.g., patterned) or may be otherwisemanufactured therein. For example, a surface holographic or diffractiveoptical element (e.g., surface relief grating) may be fabricated bypatterning (e.g., etching) a surface of the waveguide or a layerthereon. A volume holographic or diffractive optical element may also beformed by changing the index of refraction of material comprising thewaveguide or a layer disposed thereon. Accordingly, the incouplingoptical element 942 may be disposed in the volume of the waveguide 940or a layer disposed thereon. Depending on the design, the incouplingoptical element 942 may be transmissive or reflective and may operate intransmission or reflection. For example, the incoupling optical element942 may include a transmissive or reflective diffractive optical element(e.g., grating) or holographical optical element that operates intransmission or reflection, respectively, e.g., turning light that istransmitted therethrough or that is reflected therefrom.

The incoupling optical element 942 may comprise a reflective opticalelement (e.g., mirror). For example, the incoupling optical element 942may comprise an off-axis reflector. Additionally or alternatively, theincoupling optical element 942 and/or coupling optical element 944 caninclude a polarization optical element, such as a polarization selectiveturning element (e.g., polarizer). The polarization selective turningelement may include one or more polarization gratings, diffractiveoptical elements, and/or holographic optical elements and may compriseliquid crystal structures such as liquid crystal polarization gratings.For example, one or both of the incoupling optical element 942 and/orthe coupling optical element 944 can include liquid crystal polarizationgratings (LCPGs). LCPGs can provide high efficiency diffractionpotentially at broad wavelengths. Accordingly, LCPGs may be useful forincoupling optical elements 942 and/or the coupling optical element 944.The LCPG may be polarization dependent. The LCPG or other type of liquidcrystal grating, diffractive optical element, or optical element mayinclude a pattern or arrangement of molecules of liquid crystalconfigured to provide one or more functions such as turn light into awaveguide or out of a waveguide. Accordingly, incoupling optical element942 and/or the coupling optical element 944 may comprise polarizationgratings. Additionally or alternatively, incoupling optical element 942and/or the coupling optical element 944 can comprises liquid crystal andthus in some implementations one or both may be liquid crystal gratingsor liquid crystal diffractive optical elements. Additionally oralternatively, one or both of the incoupling optical element 942 and/orthe coupling optical element 944 can include a blazed grating. In somedesigns, the incoupling optical element 942 comprises a liquid crystalreflector, such as a cholesteric liquid crystal reflective lens (e.g.,reflective liquid crystal diffraction lens, Bragg-reflective structure,reflective liquid crystal diffraction grating, etc.). Some nonlimitingexamples of liquid crystal gratings, liquid crystal polarizationgratings and other liquid crystal optical elements are discussed in thefollowing published applications, each of which is hereby incorporatedby reference herein in its entirety and for all purposes: U.S.Publication No. 2018/0143438, titled “MULTILAYER LIQUID CRYSTALDIFFRACTIVE GRATINGS FOR REDIRECTING LIGHT OF WIDE INCIDENT ANGLERANGES,” filed on Nov. 16, 2017; U.S. Publication No. 2018/0143485,titled “SPATIALLY VARIABLE LIQUID CRYSTAL DIFFRACTION GRATINGS,” filedon Nov. 16, 2017; U.S. Publication No. 2018/0143509, titled “WAVEGUIDELIGHT MULTIPLEXER USING CROSSED GRATINGS,” filed on Nov. 16, 2017; U.S.Publication No. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWERREFLECTOR,” filed on Feb. 22, 2018; U.S. Publication No. 2018/0239177,titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIONCONVERSION,” filed on Feb. 22, 2018; and U.S. Publication No.2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERIC LIQUIDCRYSTAL,” filed on Dec. 7, 2017. The designs of the incoupling opticalelement 942 and/or the coupling optical element 944, however, are notlimited to these and may include other types of optical elements,diffractive optical element, liquid crystal optical element, liquidcrystal gratings and liquid crystal polarization gratings. Furtherinformation on examples of cholesteric liquid crystal structures such asreflectors may also be found below in in the section titled “CholestericLiquid Crystal Mirror.” As discussed above, other liquid crystal opticalelements as well as other non-liquid crystal optical elements may beused. Accordingly, many types of coupling optical elements (e.g.incoupling optical element 942 and/or the coupling optical element 944),diffractive optical element, gratings, polarization gratings, etc., maybe used, both those described herein as well as other types of gratings,diffractive optical elements, liquid crystal elements, and opticalelements generally. In various implementations, the incoupling opticalelement 942 may be configured to couple light from the image projector930 and/or the light source 960 into the waveguide at an angle greaterthan the critical angle so as to be guided within the waveguide 940 bytotal internal reflection to the eye to the user's eye 210.

The waveguide 940 may comprise one or more waveguides. In someimplementations, the one or more waveguides 940 comprises a stack ofwaveguides. In some designs, for example, different waveguides of thestack of waveguides are configured to output light with differentwavefront divergence as if projected from different distances from theuser's eye. For example, a first waveguide or group of waveguides may beconfigured to output light that is collimated or has a first divergenceas if projected from a first depth, and a second waveguide or group ofwaveguides may be configured to output light that is diverging (notcollimated) or is at a second divergence (greater than the firstdivergence) as if projected from a second depth closer than the firstdepth. In some designs, the different waveguides may be configured tooutput light having different associated colors. For example, a firstwaveguide may be configured to output red light, a second waveguide maybe configured to output green light, and a third waveguide may beconfigured to output blue light. A fourth waveguide may be configured tooutput and/or input infrared light.

The outcoupling optical element 952 for coupling light from thewaveguide 940 to the camera 920 such as shown in FIG. 10 may comprise,for example, a plurality of turning features configured to turn lightincident thereon at an angle such that light is not guided within thewaveguide and is turned out of the waveguide to the camera. Theoutcoupling optical element 952 may be disposed within an interior ofthe waveguide 940 or may be patterned (e.g., etched) in or on a surface(e.g., major surface) of the waveguide 940. For example, a surfaceholographic or diffractive optical element (e.g., surface reliefgrating) may be fabricated by patterning (e.g., etching) a surface ofthe waveguide or a layer thereon. A volume holographic or diffractiveoptical element may also be formed by changing the index of refractionof material comprising the waveguide or a layer disposed thereon.Depending on the design, the outcoupling optical element 952 may betransmissive or reflective and may operate in transmission orreflection. For example, the outcoupling optical element 952 may includea transmissive or reflective diffractive optical element (e.g., grating)or holographical optical element that operates in transmission orreflection, respectively, e.g., turning light that is transmittedtherethrough or that is reflected therefrom.

The outcoupling optical element 942 may comprise a reflective opticalelement (e.g., mirror). For example, the outcoupling optical element 952may comprise an off-axis reflector. In some designs, the outcouplingoptical element 952 can include a polarization optical element, such asa polarization selective turning element (e.g., polarizer). Accordingly,the polarization selective turning element may include one or morepolarization gratings, diffractive optical elements, and/or holographicoptical elements and may comprise liquid crystal structures such asliquid crystal polarization gratings. In some implementations, forexample, the outcoupling optical element 952 can include liquid crystalpolarization gratings (LCPGs). LCPGs can provide high efficiencydiffraction potentially at broad wavelengths. Likewise, LCPGs may beuseful for outcoupling optical element 952. The LCPG may be polarizationdependent. The LCPG or other types of liquid crystal gratings mayinclude a pattern or arrangement of molecules of liquid crystalconfigured to provide one or more functions such as turn light into awaveguide or out of a waveguide. Accordingly, outcoupling opticalelement 952 may comprise polarization gratings. Additionally oralternatively, outcoupling optical element 952 can comprises liquidcrystal and thus in some implementations may be liquid crystal gratingsor other liquid crystal optical element such as liquid crystaldiffractive optical elements. Additionally or alternatively, theoutcoupling optical element 952 can include a blazed grating. In somedesigns, the outcoupling optical element 952 comprises a liquid crystalreflector, such as a cholesteric liquid crystal reflective lens (e.g.,reflective liquid crystal diffraction lens, Bragg-reflective structure,reflective liquid crystal diffraction grating, etc.). Some nonlimitingexamples of liquid crystal gratings, liquid crystal polarizationgratings and other liquid crystal optical elements are discussed in thefollowing published applications, each of which is hereby incorporatedby reference herein in its entirety and for all purposes: U.S.Publication No. 2018/0143438, titled “MULTILAYER LIQUID CRYSTALDIFFRACTIVE GRATINGS FOR REDIRECTING LIGHT OF WIDE INCIDENT ANGLERANGES,” filed on Nov. 16, 2017; U.S. Publication No. 2018/0143485,titled “SPATIALLY VARIABLE LIQUID CRYSTAL DIFFRACTION GRATINGS,” filedon Nov. 16, 2017; U.S. Publication No. 2018/0143509, titled “WAVEGUIDELIGHT MULTIPLEXER USING CROSSED GRATINGS,” filed on Nov. 16, 2017; U.S.Publication No. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWERREFLECTOR,” filed on Feb. 22, 2018; U.S. Publication No. 2018/0239177,titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIONCONVERSION,” filed on Feb. 22, 2018; and U.S. Publication No.2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERIC LIQUIDCRYSTAL,” filed on Dec. 7, 2017. The designs of the outcoupling opticalelement 952, however, are not limited to these and may include othertypes of optical elements, diffractive optical element, liquid crystaloptical element, liquid crystal gratings and liquid crystal polarizationgratings. Further information on examples of cholesteric liquid crystalstructures such as reflectors may also be found below in the sectiontitled “Cholesteric Liquid Crystal Mirror.” As discussed above, otherliquid crystal optical elements as well as other non-liquid crystaloptical elements may be used. Accordingly, many types of couplingoptical elements (e.g. outcoupling optical element 952), diffractiveoptical element, gratings, polarization gratings, etc., may be used,both those described herein as well as other types of gratings,diffractive optical elements, liquid crystal elements, or opticalelements generally. As referred to above, the outcoupling opticalelement 952 may be configured to redirected light guided within thewaveguide 940 at an angle less than the critical angle so as not to beguided within the waveguide by total internal reflection but to beejected out to the camera 920.

In various designs, the coupling optical element 944 may be transparentin the visible spectrum such that the user can see through the couplingoptical element 944 and the eyepiece 950 to the environment in front ofthe user. The incoupling optical element 942 may also turn light in thevisible spectrum, for example, if the incoupling optical element is usedto receive light from the image projector 930 and/or if the illuminationsource 960 is configured to output visible light to illuminate the eye210 with visible light. In some embodiments, the incoupling opticalelement 942 is configured to turn infrared light, for example, if theillumination source 960 is configured to output infrared light toilluminate the eye 210 with infrared light. In some designs such asshown in FIG. 10 , the incoupling optical element 942 may be more medialor nasal than the outcoupling optical element 952. However, in otherdesigns the incoupling optical element 942 may be more lateral ortemporal than the outcoupling optical element 952. In certainimplementations such as shown in FIG. 10 , the outcoupling opticalelement 952 may be adjacent the incoupling optical element 942 althoughnon-adjacent positioning is possible.

The illumination source 960 may be disposed on the same side of theeyepiece 950 as the eye 210 (e.g., rearward or proximal side), as shownin FIG. 10 . (Proximal may refer to the side closest to the eye 210.)Alternatively, the illumination source 960 may be disposed on the sideopposite the eye 210 (e.g., forward or distal side). The illuminationsource 960 may be configured to direct light into at least one of themajor surfaces of the waveguide 940 via the incoupling optical element942. The light source 960 may be configured to emit invisible light(e.g., infrared). The light source 960 may include one or more LEDs. TheLEDs may comprise infrared LEDs. The light source 960 may be configuredto emit coherent light. In some designs, the light source 960 comprisesa laser (e.g., infrared laser). In some designs, the light source 960emits pulsed light. For example, the camera 920 can be configured tocapture an image periodically. Accordingly, the illumination source 960can be pulsed to coincide with the period during which the cameraobtains images. The intensity output from the illumination source 960can be reduced when the camera is not obtaining an image. Byconcentrating the total energy of the illumination on a short timeincreased signal to noise can be obtained while not exposing the eye 210to unsafe intensity levels. In some cases, for example, the camera 920captures one image every 30 milliseconds and the exposure time of thecamera is few milliseconds. The illumination source 960 can beconfigured to output pulses having similar period and duration to matchthat of the camera 920.

In some implementations, different light sources having differentwavelengths are alternately pulsed to provide different wavelengthillumination at different times as discussed below.

The incoupling optical element 942 may be in direct opticalcommunication with the illumination source 960 and/or image projector930, for example, so as to guide light from said image projector 930and/or light source 960 therein. For example, light emitted by the lightsource 960 may be incident on the incoupling optical element 942 beforeoptically interacting with either the coupling optical element 944and/or outcoupling optical element 952.

As shown in FIGS. 11A-11E, light 902 projected from the image projector930 may form an image on the retina. The image projector 930 may includea light source, a modulator, and/or projection optics. The light sourcefor the image projector 930 may comprise one or more LEDs, lasers orother light sources and may comprises one or more visible light sources.The modulator may comprise a spatial light modulator such as a liquidcrystal spatial light modulator. Such a spatial light modulator may beconfigured, for example, to modulate the intensity of light at differentspatial locations. The projection optics may comprise one or morelenses. Other types of image projectors 930 capable of projecting and/orforming images may be employed. For example, the image projector 930 maycomprise a scanning optical fiber.

The image projector 930 and the incoupling optical element 942 may be indirect optical communication with each other. The image projector 930may, for example, be aligned with the incoupling optical element 942into which light from the image projector 930 is directed. In somecases, image projector 930 is disposed adjacent the correspondingincoupling optical element 942 and/or the waveguide 940. The imageprojector 930 may also be disposed in an optical path that includes theincoupling optical element 942, the coupling optical element 944, andthe eye 210.

The image projector 930 may be a separate element than the illuminationsource 960, as shown in FIG. 10 as well as in FIGS. 11A-11E. However, insome cases the image projector 930 may be used as the illuminationsource. For example, in addition to injecting images into the eye 210,the image projector 930 may be used to direct visible and/or infraredlight into the eye to illuminate the eye for image capture.Alternatively, however, one or more separate light sources 960 may beused to illuminate the eye 210 for image capture.

The light emitted by the illumination source 960 may comprise aparticular wavelength range of light such as, for example, invisiblelight. The illumination source 960 may be configured to projectinvisible (e.g., infrared) light onto/into the eye 210 for imaging oneor more parts (e.g., cornea, retina) of the eye 210. In certain exampleimplementations, the light source 960 may be configured to emit light inthe range of between about 850 nm and 940 nm. The light source 960 maybe configured to emit light extending over a wavelength range of atleast about 20 nm. Other ranges are also possible. The wavelength rangeemitted may be 5 nm, 10 nm, 15 nm, 50 nm, 75 nm, 100 nm, 150 nm, 200 nm,or any range between any of these values. The light source 960 may beconfigured to emit light across a broad band of wavelengths, such as anyrange within the infrared spectrum.

The imaging device 920, which may comprise a camera, may comprise adetector array and possibly imaging optics. The detector array maycomprise, for example, a CCD or CMOS detector array and the imagingoptics may comprise one or more lenses. The one or more lenses may havepositive optical power and an associated focal length. In certaindesigns, the camera 920 is focused at infinity. For example, the opticsmay have a focal length, f, and detector array may be disposed adistance away from the optics corresponding to the focal length suchthat objects at a large distance are imaged onto the detector array.Similarly, light from the eye or objects in the environment that iscollimated will be focus on the detector array to form an image of theeye or object thereon.

The imaging device 920 may be disposed on the opposite side of thewaveguide 940 as the illumination source 960 and/or the eye 210. In somedesigns, the imaging device 920 may be disposed on the same side of thewaveguide 940 as the light source 960 and/or eye 210. As shown in FIG.10 , the imaging device 920 may be disposed near a lateral or temporaledge of the eyepiece 950 although other locations are possible.

FIGS. 11A-11E illustrate the operation of the example imaging system 900of FIG. 10 . FIG. 11A shows the illumination source 960 emitting light902 toward the incoupling optical element 942 on the waveguide 940. Asshown, the light 902 can be directed generally at normal incidence tothe eyepiece 950 although other angles are possible. In some designs,the light source 960 is configured to emit collimated light into theeyepiece 950. As shown in FIG. 11B, the illumination light 902 can becoupled into the waveguide 940 via the incoupling optical element 942.In some designs where the incoupling optical element 942 comprises adiffractive optical element (e.g., grating, holographic element) thelight incident thereon is diffracted at an angle greater than thecritical angle of the waveguide to cause the incoupled light 904 to beguided within the eyepiece 950 by total internal reflection (TIR). Insome designs, the incoupling optical element 942 may be configured todirect light toward the coupling optical element 944. The incouplingoptical element 942 may be polarization selective. For example, theincoupling optical element 942 can include a polarization selectiveturning element such a polarization grating like a liquid crystalpolarization grating. FIG. 11C shows how the incoupled light 904propagating through the waveguide 940 by TIR.

FIG. 11D illustrates an example imaging system 900 coupling light out ofthe eyepiece 950. As the incoupled light 904 propagates through thewaveguide 940, some of the light may be incident on the coupling opticalelement 944. The coupling optical element 944 can be configured tocouple the incoupled light 904 out of the eyepiece 950 and toward theuser's eye 210. The coupling optical element 944 may be configured tocouple the light as collimated light toward the eye 210. The couplingoptical element 944 may be tuned to light of a particular wavelengthrange. For example, the coupling optical element 944 may be configuredto couple infrared light (e.g., between about 700 nm and 15000 nm) outof the waveguide 940. In some designs, the coupling optical element 944can be configured to couple multiple wavelengths of light out of theeyepiece 950. For example, the coupling optical element 944 may be tunedfor both infrared and visible light. The coupling optical element 944can also be configured to couple light into the waveguide 940, asdescribed more fully below.

The coupling optical element 944 can be configured to increase one ormore dimensions of an eyebox for a user. For example, the one or moredimensions may be measured along a first axis (e.g., x axis). Theeyepiece 950 may further include an orthogonal pupil expander (OPE). TheOPE may have at least one light redirecting element disposed on or inthe waveguide (e.g., on one of the major surfaces) or the OPE may bedisposed within the waveguide 940. The OPE may include features similaror identical to those described above for light distributing elements730, 740, 750 above. In some implementations, the light redirectingelement may comprise a diffractive optical element. The OPE may beconfigured to increase a dimension of the eyebox along a second axis(e.g., y axis) orthogonal to the first axis.

FIG. 11D shows some of the light exiting the eyepiece 950 toward theuser's eye 210. In some designs, the coupling optical element 944 isconfigured such that incoupled light 904 that is incident on thecoupling optical element 944 at various portions of the coupling opticalelement 944 along the first axis (e.g., parallel to the x-axis) exitsthe eyepiece 950 at each portion of the coupling optical element 944along the first axis. This may provide a user with a light forprojecting images or illuminating the eye for different eye positions orlocations.

As shown in FIGS. 11D-11E, the coupling optical element 944 may beconfigured to couple the incoupled light 904 out of the eyepiece 950 ascollimated light. This light may also be directed in general near normalrelative to a major surface of the eyepiece 950 and/or waveguide 940.The collimated light may be directed into the eye and focus by the eye(e.g., the cornea and natural lens of the eye) onto the retina. Thislight 908 incident on the retina may be provide illumination for imagingthe retina and/or providing image content to the eye. Some of this light908, for example, may be reflected or scatter off the retina, exitingthe eye and providing for images of the retina to be captured. The lightsource 960 may be an extended light source such that the light willilluminate a region of the retina.

FIGS. 12A-12E illustrate how the imaging system 900 of FIGS. 11A-11E mayadditionally or alternatively be used for image collection of the eye210. FIG. 12A shows light 910 reflected from the retina exiting the eye210. As shown, the light 910 scattered or reflected from the retina thatpasses through the natural lens of the eye, the pupil in the eye and thecornea from may be collimated. This light may also be incident on theeyepiece 950 at normal incidence (e.g., at a right angle to a majorsurface of the waveguide 940 and/or coupling optical element 944). Thecoupling optical element 944 may be configured to couple the light 910reflected from the retina into the waveguide 940.

FIG. 12B illustrates an example imaging system 900 as it couples lightinto the eyepiece 950. The coupling optical element 944 may include aturning feature such as a diffractive optical element, or otherstructures that redirect the light at an angle greater than the criticalangle so as to be guided within the waveguide 940. The coupling opticalelement 944 may be configured to direct the incoupled light 914generally toward the light source 960 and/or the imaging device 920. Thecoupling optical element 944 can be configured to couple less than afraction of this light propagating toward the camera 920 back out of thewaveguide 940. For example, a partially reflective element (e.g.,semi-transparent mirror) may be disposed on or in the waveguide 940 suchthat a portion of the incoupled light 914 continues to propagate withinthe waveguide 940 by total internal reflection while reducing leakage ofthe incoupled light 914 out of the waveguide 940 along portions of thewaveguide 940 where the coupling optical element 944 is disposed. Theportion of light that does not leak out may be any fraction between 0and 1. For example, the portion may be 0.90, where 90% of the light rayspropagating through the waveguide 940 along the coupling optical element944 are maintained within the waveguide 940 at each reflection of thelight rays. Other portions are possible (e.g., 0.10, 0.20, 0.30, 0.40,0.50, 0.60, 0.70, 0.80, or any range between any of these values). Suchpartially reflective element(s) can similarly be used in implementationsdescribed below.

As shown in FIG. 12C, collimated incoupled light 914 may continue topropagate through the waveguide 940 toward the imaging device 920. FIG.12D shows how some of the incoupled light 914 can continue to propagateuntil it is incident on one or more outcoupling optical elements 952. Inorder to reduce the amount of leakage of incoupled light 914 out of theincoupling optical element 942, the incoupling optical element 942 canbe configured to couple little of this light propagating toward thecamera 920 back out of the waveguide. For example, a partiallyreflective element (e.g., semi-transparent mirror) may be disposed on orin the waveguide 940 such that the a portion of the incoupled light 914continues to propagate within the waveguide 940 by total internalreflection while reducing leakage of the incoupled light 914 out of thewaveguide 940 along portions of the waveguide 940 where the incouplingoptical element 942 is disposed. The portion of light that does not leakout may be any fraction between 0 and 1. For example, the portion may be0.90, where 90% of the light rays propagating through the waveguide 940along the coupling optical element 944 are maintained within thewaveguide 940 at each reflection of the light rays. Other portion may bepossible (e.g., 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or anyrange between any of these values). Such partially reflective element(s)can similarly be used in implementations described below.

As shown in FIG. 12E, the outcoupling optical element 952 can beconfigured to couple light guided within the waveguide 940 out of thewaveguide 940 and to the imaging device 920. As a result, lightpropagating in the waveguide 940 that is incident on the outcouplingelement 952 may be redirected so as to be ejected out of the waveguide940, for example, out of a major surface of the waveguide 940 (e.g., theforward or rearward side of the waveguide 940) and directed on theimaging device 920. The outcoupling optical element 952 may beconfigured to direct the light 926 to exit the waveguide 940perpendicular (e.g., normal) to the major surface of waveguide 940. Insome designs, the outcoupling optical element 952 is configured todirect collimated light 924 onto the imaging device 920 at normalincidence to a light sensitive portion of the imaging device 920. Asdiscussed above, the camera 920 may be infinity focused, for example,the imaging optics may be configured to focus collimated light onto thedetector array.

Accordingly, the waveguide 940 may be configured to guide light coupledfrom the user's eye 210 into the waveguide 940 to be received by theimaging device 920 (e.g., camera) so as to capture an image of at leasta portion of the eye 210 of the user. The same waveguide 940 may beconfigured to guide light coupled from the image projector 930 such thatlight from the image projector 930 can be directed to the user's eye 210such that the image from the image projector 930 is in the vision fieldof the user. In some implementations, the same waveguide is configuredto guide light coupled from the illumination source 960 such that lightfrom the illumination source can be directed to the user's eye 210 toilluminate the eye such that an image of the eye can be captured by thecamera 920.

In some implementations, the same coupling optical element 944 can beconfigured to (i) couple light from the user's eye 210 into thewaveguide 940 to be received by the imaging device 920 and (ii) couplelight from the image projector 930 out from the waveguide 940 to theuser's eye 210 to project image content into the user's vision field. Insome implementations, the same coupling optical element 944 can beconfigured to couple light from the illumination source 960 out of thewaveguide to the user's eye 210 such that light from the illuminationsource can illuminate the eye.

In other designs, different waveguides can be used and/or differentcoupling optical elements 944 can be used. In some designs for example,a first waveguide 940 may be configured to guide light coupled from theuser's eye 210 to be received by the camera 920 so as to capture animage of at least a portion of the eye 210 of the user and a secondwaveguide may be configured to guide light coupled from the imageprojector 930 such that light from the image projector 930 can bedirected to the user's eye 210. The first and second waveguides may bestacked on top of one another. Another waveguide may in addition or inthe alternative be configured to guide light coupled from theillumination source 960 such that light from the illumination source canbe directed to the user's eye 210 to illuminate the eye.

Also, in some implementations, a first coupling optical element 944 canbe configured to (i) couple light from the user's eye 210 into thewaveguide 940 to be received by the imaging device 920 and (ii) couplelight from the image projector 930 out from the waveguide 940 to theuser's eye 210 to project image content into the user's vision field.Another coupling optical element may in addition or in the alternativebe configured to coupled light from the illumination source 960 out ofthe waveguide to the user's eye 210 such that light from theillumination source can illuminate the eye.

In some designs, the coupling optical element 944 can include aplurality of diffractive optical elements (DOEs). For example, a firstDOE can be configured to couple light from the user's eye 210 into thewaveguide 940 to be received by the imaging device 920. A second DOE canbe configured to couple light from the image projector 930 out of thewaveguide 940 to the user's eye 210 to project image content into theuser's vision field. Optionally, a third DOE can be configured to couplelight from the light source 960 out of the waveguide 940 to the user'seye 210 to illuminate the eye. The first and second (and possibly third)DOEs can be stacked, e.g., in some implementations such that light fromthe environment in front of the user passes through the first DOE and isthen incident on the second DOE and then incident on the third DOE andincident on the user's eye. The order, however, may be different.

In some designs, the first and second DOEs are integrated in a singleelement or volume of the waveguide 940. In some implementations, forexample, both the first and second DOEs are superimposed on each other(e.g., occupy the same or approximately the same volume) within thewaveguide 2102. For example, the first and second DOE may be recorded inthe same medium.

As described above, image capture of the eye, e.g., of the retina, canfacilitate eye tracking. FIG. 13A, for example, illustrates the imagingsystem 900 configured to image various portions of the eye 210 (e.g.,retina), for example, at different times when the eye is in differentpositions. Stages A and B may refer to images of the eye 210 duringdifferent orientations of the eye. FIG. 13A shows imaging of the eye 210and the results thereof during both stage A and stage B imaging.

In some implementations, the light emission 928 (e.g., from anillumination source 960 such as described above or from one or moreilluminations sources configured and/or located differently) can be usedto obtain one or more images of the retina 962, as shown by FIG. 13A.The image of the retina 962 may comprise one or more regions 964, 966that are imaged during different orientations of the eye 210. FIG. 13Ashows two regions 964, 966 of the image of the retina 962. For example,the region 964 of retina imaged in stage A may be imaged while the eye210 is directed at an angle normal to the waveguide 940. The image datafor the region 966 of retina imaged in stage B may be obtained while theeye 210 is oriented at an acute angle with the waveguide 940. Using oneor more orientations of the eye 210 during one or more stages ofimaging, a composite image or map of the retina 962 may be obtained.Processing electronics or a processor, such as data module 140 (see FIG.2 ), may be used to find overlapping image data between two neighboringregions. Using the overlapping regional image data, a composite image orof the retina 962 can be determined. A larger size (e.g., full-size)composite image or map of the user's retina can be stored.

As described herein, the head mounted display can be used to map auser's eye retina based on the direction that user's eye is directed. Toprovide a realistic and intuitive interaction with objects in the user'senvironment using eye gaze and/or to identify a wearer of the headmounted display device, the head mounted display system can use retinalmapping to incorporate a uniqueness of a user's eye features and otherconditions that may have some effect on eye measurements. For example,the images may be identified based on positions of blood vessels in thecorresponding retinal image.

Retinal mapping can involve a process for enabling a computing device tolearn how to associate a user's eye gaze (e.g., as identified in retinalimages) with gaze points in a 2D or 3D space. An eye gaze may beassociated with a single point in the 2D or 3D space. An eye gaze canalso be associated with multiple points in the space, which can describea movement of a virtual object (e.g., a series of points, a location ofa moving image).

The head mounted display system can determine a user's eye gaze based onretinal images. The head mounted display system can obtain retinalimages using sensors (e.g., eye cameras such as the imaging device 920).The head mounted display system can image one or both eyes of the userwhile the user changes his or her eye gazes (such as, e.g., when theuser is looking around to follow a moving or shifting calibration targetor fixation target). To map a user's retina, the head mounted displaysystem can present a virtual target, e.g., a fixation target, for theuser to look at. The virtual target may be associated with one or moreknown points of gaze in the 2D or 3D space. While the user is looking atthe target, the head mounted display system can acquire retinal image(s)and associate the image(s) with gaze point(s). The head mounted displaysystem can calculate and/or generate a mapping matrix based on theassociations of respective retinal images and points of gaze associatedwith the target.

The retinal mapping result can reflect uniqueness in each person's eyes.For example, the head mounted display system can generate a mappingmatrix customized to one or both eyes of a specific individual. Forexample, the users may have different amounts of eye movements or eyegazes in response to a specific target. Additionally or alternatively,the user may have a different position, size, shape, and/or orientationof blood vessels in the retina. As a result, by generating a calibrationresult specific to an individual user, the head mounted display systemmay allow more accurate user interactions with eye gazes and/or mayallow for identification a particular user.

Accordingly, when a user puts on the head mounted display device, thesystem can detect whether the user is a previous user or a new user. Aconfusion matrix can be calculated where a score for a particular eyegaze image stored in the system memory is compared to a correspondingimage of the current user. The confusion matrix can include a comparisonscore for a plurality of eye gazes and associated retinal images. Basedon the comparison scores, the system may be able to make a determinationwith regard to an identity of the user (e.g., whether the user is thesame as the individual for which the stored retinal images or compositemap are associated) and/or a confidence level for the determination. Theconfidence level may, for example, include an identity coefficient.Stored images, for example, a composite image or map, may be comparedwith later obtained images referred to as instantaneous or real-timeimages obtained for a current user. The system may provide an alert ifthe system detects that the user is a new user or may take other action.

The system may apply filtering such as digital filtering or imageprocessing to the images of the retina captured by the camera. Suchfiltering or imaging processing, may for example, enhance features thatmay be used for identification, stitching, assembling a compositeimages, eye tracking, etc. Such filtering or image processing maycomprise edge enhancement. Such a filter may comprise, for example, aFrangi filter although other types of filters may be used. Such a filteror processing (e.g., edge enhancement or a Frangi filter) can be used toenhance and/or detect images features such as vessels or tubularstructures or fibers in retinal images.

FIG. 13B illustrates a pattern of sequentially displayed fixationtargets that can be used in the retinal mapping process. These virtualtargets on which a user's eye will direct their gaze can cause the eye'sgaze to be redirected to a variety of different directions during whichthe retina can be imaged. The resultant images associated with thedifferent gaze directions correspond to non-identical portions of theretina. As discussed above, when the eye is gazing in differentdirections to view differently located fixation targets on the display,images captured by the camera include different portions of the retina.These images can be assembled to form a larger map or composite image ofthe retina.

FIG. 13B shows a virtual target at sixteen different location in auser's field of view (FOV) 1200. In various implementations, the virtualtarget would be presented at a given location at a given time. One ormore retinal images would be obtained during a time when the virtualtarget is presented at that particular location to a user. This image orthese images may be associated with that target position and/or acorresponding gaze direction. Greater or fewer target locations may beused. In the example shown in FIG. 13B, the sixteen targets locations1202 a-1202 p are shown. More or less target locations may be used. Thetarget locations may also be different. The order at which the targetsare presented at the different locations may vary. For example, thetarget may move in a raster pattern from the left to the right side ofthe field of view of the user, back to from the right to the left, andagain from the left to the right, lowering the position of the target inthe field of view with each lateral pass across the field of view.However, other patterns and approaches are possible. Likewise, thetarget can be rendered identically or differently at the differentlocations. For example, the target rendered may be different sizes,shapes, colors, etc. The targets can be rendered sequentially to a userduring the eye tracking calibration process. For example, as discussedabove the head mounted display system may render target in a serpentinepattern. For example, the target 1202 a may be followed by 1202 b, then1202 c, then 1202 d, then 1202 h, then 1202 g, and so forth. Otherpatterns are possible. For example, the target could be displayed inmore random or non-sequential patterns. In some embodiments, a singletarget is displayed to the user, and the target moves around the user'sfield of view (for example, passing or temporarily stopping at thepositions 1202 a-1202 p during the target's movement). The head mounteddisplay system can acquire an image of the user's retina(s) while theuser is looking at these targets. For example, the head mounted displaysystem can acquire a first image when the user is looking at the targetat the first location 1202 a while acquiring a second image when theuser is looking at the target at a second location 1202 b, and a thirdimage when the user is looking at the target at a third location 1202 c,and so forth. The wearable system can associate the first image to thefirst position 1202 a and associate the second image with the secondposition 1202 b, and the third image with the third position 1202 c, andso forth. Neighboring images may be stitched together in a database tocreate a full or partial retinal map. For example, two image can bestitched together in appropriate registration using features or portionsof the feature (e.g., blood vessels or portions thereof) that are commonto the multiple images. In various implementations, adjacent targetpositions would produce overlapping images that can be registered andstitched together. For example, target position 1202 a and targetposition 1202 b as well as target position 1202 b and target position1202 c may produce overlapping and adjacent retinal images that can bestitched with each other. Accordingly, a number of different retinalimages may be obtained with different eye gazes so as to assemble alarger image (e.g., a composite image or map) of the retina.

As discussed above, eye tracking can be performed using the compositeretinal image or map. For example, after the target is no longerdisplayed, the user may move their eye gaze about as the user looks atdifferent real objects in front of the user and head mounted display oraugmented reality (virtual) image content displayed by the head mounteddisplay. One or more retinal images may be obtained at these times. Theterm “instantaneous” or “real-time” images may be used herein todescribe these images obtained subsequent to calibration that can beused for eye tracking (or other purpose such as obtaining biometricdata). These “instantaneous” or “real-time” images likely correspond toa portion of the composite retinal image or map. The system may beconfigured to sufficiently match this “instantaneous” or “real-time”retinal image with a portion of the composite retinal image or retinalmap. Such matching may be based on features or portions of features(blood vessels or portions thereof) that are common to both the“instantaneous” or “real-time” retinal image and the portion of thecomposite retinal image or map. Based on the location the portion of thecomposite retinal image or map to which this “instantaneous” or“real-time” retinal image coincides, a gaze direction may be deduced.Different gaze directions will result in retinal images that correspondto different portions of the retinal map. Accordingly, identifying thelocation of the “instantaneous” or “real-time” retinal image on thecomposite retinal image or map will provide information as to thedirection of the user's gaze. Eye tracking, for example, tracking themovement of the eye and the change in eye gaze may be performed usingsuch or similar methods. As discussed above, edge enhancement, edgedetection, or other digital filtering and/or processing may be used toenhance and/or correlate features of different images with the compositeretinal image or retinal map.

In various implementations after completion of the initial calibrationprocess where the virtual target or fixation target is displayed (e.g.,at a plurality of locations) to assemble a composite retinal image ormap, the composite retinal image or map can still be refined. Forexample, as additional retinal images are obtained, the compositeretinal image or map can be further refined or improved using theadditional images. Accordingly as additional “instantaneous” or“real-time” retinal images are obtained, for example for the purpose ofproviding eye tracking, the composite retinal image or map can befurther refined or improved using the “instantaneous” or “real-time”. Asa user continues to look at various positions in the display (with orwithout aid of a calibration target), the retinal composite image or mapmay be further refined using additional images are acquired subsequentto the initial calibration where the virtual target or fixation targetwas displayed. The quality of the composite retinal image or map maytherefore be increased.

Additional non-limiting examples of how eye tracking may be accomplishedand/or a composite retinal image or map may be produced and retinalimages used are described in U.S. Publication No. 2017/0205875, titled“EYE IMAGE COLLECTION,” filed on Jan. 17, 2017, the disclosure of whichis hereby incorporated herein by reference in its entirety.

Accordingly, as discussed above larger portions of the retina may berecorded and mapped by obtaining retinal images and/or other images ofthe eye using imaging systems such as described herein and such imagesmay facilitate eye tracking. For example, an image of the eye 210 shownin FIG. 13A may be captured when the eye is in an arbitrary position.The processing electronics or a processor (such as the same or differentone described above as forming the composite image) may then comparecaptured images of the user's retina in real time to the storedcomposite or larger size (e.g., full-size) image of the user's retina totrack eye movement. A given image of the user's retina captured in realtime may show a specific portion of the user's retina. As describedabove, by comparing such a captured image to the stored image of theuser's mapping a larger portion of the user's retina, the system candetermine which portion of the user's retina is shown in the capturedimage, and can thereby determine the position/orientation of the eyethat would produce such an image. See for example FIG. 13A, which showstwo different images of portions of the retina that are produced whenthe eye is in two different positions and/or orientations. Accordingly,the position and/or orientation of the eye may be determined bycapturing different images of the retina and determining which portionof the retina is visible. Such determination may be performed even if acomposite image is not formed but rather multiple images of the retinafor different eye positions/orientations are recorded and stored in adatabase. When a future image of the retina is obtained, that image maybe compared to images in the database of stored images to determinewhich image in the database resembles the image of the eye recentlyobtained. Matching the recent image to one or more of the images in thedatabase having associated positions and/or orientations associated withthem can enable determination of the orientation and/or position of themore recent image. Other approaches to eye tracking may be used based onthe images captured using the designs described herein.

As described herein, the retinal images may be employed for otherpurposes as well. For example, the retinal images may be used to verifythat the user is the same user for which the composite retinal image ormap was obtained. An image of the retina that is obtained when a user iswearing the head mounted display system (e.g., during the calibrationprocess and/or during later use) may be compared with a previouslyobtained composite retinal image or map (e.g., created a prior day orwhen the head mounted display was previously booted up) that is stored.If the recently obtained retinal image does not match a portion of thecomposite retinal image or map sufficiently enough, a conclusion may bemade that the current user is different than the previous user (e.g.,for which the composite virtual image or map was created). Such methodsmay be used for security, e.g., to verify that the current user of thehead mounted display device is the owner or typical user of the device.Accordingly, bioimetric data obtained via retinal imaging may be usedfor security purposes.

The retinal imaging may be used as well to collect biometric data formonitoring the user's health. Medically related data may be obtainedfrom the retinal images. Such medical data may be useful for monitoringthe health of the user.

Although various applications of eye imaging, such as eye tracking,collection of biometric data for heath monitoring and for security arediscussed herein in the context of retinal imaging, imaging other partsof the user, for example, of the user's eye may be employed for theseand other purposes.

Although the eyepiece 950 is described above as capable of beingutilized to facilitate imaging of the eye, the eyepiece can also be usedto image the world in front of the user. FIGS. 14A-14B, for example,illustrate an example imaging system 900 that can be used to image aportion of an environment in front of the user and/or objects in theportion of the environment. The imaging system 900 used may be a similarsystem as described for FIGS. 11A-11E and/or for FIGS. 12A-12E exceptthat light is collected by the eyepiece 950 from the environment forwardthe eyepiece and the user. FIG. 14A, for example, illustrates light 970from the environment that is reflected off and/or emitted by one or morephysical objects 972 in the environment forward the user and eyepiece950. As shown, the light 970 from the environment may be approximatelycollimated (e.g., at infinity), for example because the physical object972 in the environment may be located at a sufficiently large distancefrom the imaging system 900 for the light rays reaching the imagingsystem 900 to be collimated or approximately collimated. In someimplementations, the imaging system 900 may be configured to image theenvironment and/or objects in the environment without the use of anyoptical elements having optical power (e.g., lenses, mirrors) in theimaging system 900.

The imaging system 900 shown in FIGS. 14A and 14B is similar to theimaging systems described above. The imaging system includes theeyepiece 950 comprising one or more waveguides 940 including thecoupling optical element 944 configured to direct light from an imageprojector 930 (not shown) into the eye 210 to form images therein. Theone or more waveguides may include a plurality of waveguides (e.g., astack of waveguides) configured to incouple/outcouple a plurality ofcorresponding colors/wavelengths. Each waveguide in a stack ofwaveguides may be configured to direct light of a particular color(e.g., red, green, blue). For example, a distalmost waveguide (e.g.,stack of waveguides) may be configured for visible light (e.g., red,blue, green) such that the waveguide is configured to incouple andoutcouple the same wavelength(s) of visible light. Additionally oralternatively, a waveguide configured to incouple and outcoupleinvisible (e.g., infrared) light may be disposed proximal the eye 210.Such a plurality of waveguides corresponding to the waveguide 940 may beused in any other implementation described herein. The imaging system900 may also include the imaging device (e.g., camera) 920 andoutcoupling optical element 952 configured to turn light reflected fromthe eye 210 that is propagated within the waveguide 940 to the camera.In FIGS. 14A and 14B, the illumination source 960 is excluded since anillumination source may not be needed to image the environment in frontof the user. However, an illumination source (e.g., the light source 960described above) may be used in certain designs.

The eyepiece 950, waveguide 940, coupling optical element 944,outcoupling optical element 952 and camera 920 may be the same orsimilar to that describe above. For example, the coupling opticalelement 944 may be in physical engagement with the waveguide 940. Forexample, the coupling optical element 944 and/or outcoupling opticalelement 952 may be disposed in an optical path between the environmentin front of the eyepiece 950 and camera 920 such that light from theenvironment is coupled into the waveguide 940 via the coupling opticalelement 944 and coupled out of the waveguide via the outcoupling opticalelement to be incident on the camera 210 (for example to form an imageof at least a portion of the environment). The coupling optical element944 may comprise a plurality of turning features configured to turnlight guided within the waveguide out of the waveguide or turn lightincident on the coupling optical element 944 at an angle into thewaveguide to be guided therein by total internal reflection. Theoutcoupling optical element 952 may comprise a plurality of turningfeatures configured to turn light (from the environment) that is guidedwithin the waveguide at an angle such that the light is not guided inthe waveguide by total internal reflection but is direct out toward thecamera. The coupling optical element 944, outcoupling optical element952 and the turning features associated with each may be in physicalengagement with the waveguide 940. For example, the coupling opticalelement 944 and/or outcoupling optical element 952 may comprise one ormore holographic or diffractive optical elements (e.g., surface reliefgratings) patterned (e.g., etched) in or on the waveguide 940. Thecoupling optical element 944 and/or outcoupling optical element 952 maycomprise a layer disposed on the waveguide 940 or may be formed be inthe waveguide 940. For example, a volume holographic or diffractiveoptical element may be formed by changing the index of refraction ofmaterial comprising the waveguide or a layer disposed thereon.Accordingly, the coupling optical element 944 and/or outcoupling opticalelement 952 may be disposed in the volume of the waveguide 940 or alayer disposed thereon. Depending on the design, the coupling opticalelement 944 and/or outcoupling optical element 952 may be transmissiveor reflective and may operate in transmission or reflection. Forexample, the coupling optical element 944 and/or outcoupling opticalelement 952 may include a transmissive or reflective diffractive opticalelement (e.g., grating) or holographical optical element that operatesin transmission or reflection respectively, e.g., turning light via thatis transmitted therethrough or that is reflected therefrom. The couplingoptical element 944 and/or outcoupling optical element 952 can include apolarization optical element, such as a polarization selective turningelement (e.g., polarizer). The polarization selective turning elementmay include one or more polarization gratings, diffractive opticalelements, and/or holographic optical elements and may comprise liquidcrystal structures such as liquid crystal polarization gratings. In someimplementations, the reflective optical element may include a reflector(e.g., mirror). Other elements, such as for example the waveguide 940may be similar to that described above as well.

FIG. 14B illustrates the operation of the imaging system 900 shown inFIG. 14A. Light 970 from the environment is coupled by the couplingoptical element 944 into the waveguide 940. The coupling optical element944 may be configured to turn collimated light at an angle that isgreater than the critical angle of the waveguide 940 such that at leasta portion of this collimated light is guided within the waveguide bytotal internal reflection toward the camera 920. The outcoupling opticalelement 952 can be configured to receive at least a portion of the lightfrom the environment in front of the user that is coupled into thewaveguide 940 via the coupling optical element 944 and guided therein.The outcoupling optical element 952 may be configured to couple theincoupled light out from the waveguide 940 to the camera 920 such thatimages of the environment may be captured by the camera 920. The imagesof the environment may be passed to processing electronics, (e.g., oneor more processors), such as data module 140 (see FIG. 2 ). The datamodule 140 may be configured to reproduce a modified image of theenvironment in an augmented reality context. The processing electronicsmay be in communication with the camera 920 via a wired or wirelesselectronic signal. Additionally or alternatively, the processingelectronics may communicate with the camera 920 using one or more remotereceivers. The processing electronics may reside remotely (e.g., cloudcomputing devices, remote server, etc.).

This imaging system 900 may therefore be used for directly imaging theenvironment, which may be useful for a variety of reasons. For example,imaging the environment can be used to determine where to placeaugmented reality image content with respect to objects in theenvironment. For example, imaging the environment may provide thelocation of a table such that the head mounted display may render animage of person standing next to the table instead of on the table or inthe table. The imaging system 900 described for imaging the environmentmay also be used to image the eye 210, such as is described for FIGS.10, 11A-11E, and/or 12A-12E.

It may be desirable to image a wide view of the environment using theimaging system 900. FIG. 14C schematically illustrates an imaging system900 for collecting light from the environment using a powered opticalelement or lens such as refractive optical element 980 (e.g., a widefield of view lens) forward the eyepiece. The refractive optical element980 may have a positive optical power. The refractive optical element980 (e.g., positive lens) converges collimated light 970 from theenvironment toward the waveguide 940. Other types of lenses than thelens shown in FIG. 14C may be employed. Light that is transmitted (notshown) may pass through a powered optical element or lens such asrefractive optical element 990 (e.g., negative lens) that is configuredfor a negative power equal and opposite of the refractive opticalelement 980. The negative lens 990 may have a similar or the sameoptical power as the positive lens 980 to offset or counter the opticalpower of the positive lens or a portion thereof. In this way, light fromthe environment (e.g., distal of the waveguide 940) may pass through thenegative lens 990, the eyepiece 950, and the positive lens 980 withsubstantially no net change in optical power introduced by these twolenses to the eye. The negative lens 990 may be configured to offset orcounter the optical power of the positive lens 980 such that a user'swill not experience the power of the positive lens when viewing theenvironment in front of the eyepiece 950. The negative lens 990 willalso counter the effect of the positive lens 980 to invert images ofobject in the environment in front of the wearer. Some light 970 fromthe environment may be incoupled into the waveguide 940 by the couplingoptical element 944, in spite of some of the rays of light beingconvergent. The incoupled light incident on the outcoupling opticalelement 952 may be ejected out of the waveguide 940.

Implementations (e.g., those described by FIGS. 14A-14C) may be usedoutside an augmented reality context. For example, it is intended thatan imaging system 900 configured to image the environment be implementedwithin a wearable device, such as, for example, eyeglasses (includingunpowered glasses) or bifocals. Such an imaging system 900 may notrequire an image projector 930 and/or light source 960. Additionally oralternatively, such an imaging system 900 may not require an incouplingoptical element configured for a corresponding image projector 930and/or light source 960.

It may be advantageous to implement such an imaging system 900 forimaging the environment on a viewing screen (e.g., television screen,computer screen), such as a handheld device (e.g., cell phone, tablet).The imaging system 900 could improve video chat capabilities. Forexample, a viewer who is seeing a chat partner look into the screen mayappear to be looking directly at the viewer. This would be possiblesince the light rays captured by the imaging system 900 would becaptured in the same region where the user is looking (e.g., as opposedto viewing a screen but having the light rays captured by a separateoutward-facing camera positioned at a different location).

In implementations where the imaging system 900 of FIG. 14C is also usedto image the eye 210, a light source 960 and/or image projector 930 maybe configured to inject light into the waveguide 940. Because the lightreflected from the eye that is incoupled into the waveguide will passthrough the refractive optical element 990 (e.g., negative lens), apositive powered refractive optical element may be disposed between thelight source 960 and/or image projector 930 and between the waveguide940. The positive lens can be configured to offset or counter anyoptical power provided by the refractive optical element 990 before theincoupled light from the light source and/or light projector is incidenton the eye 210. Other types of lenses than shown in FIG. 14C may be usesas the optical element 990. Alternatively or additionally, processingelectronics in communication with the light source and/or imageprojector can be configured to alter an image sufficient to present tothe user an undistorted image after the light has passed through therefractive optical element 990. Corresponding incoupling opticalelement, outcoupling optical element, and/or coupling optical elementmay be configured to operate on non-collimated light (e.g., divergent,convergent light) in some designs.

In various implementations, the same waveguide 940 may be used to (i)propagate light from the environment in front of the eyepiece 950 andthe user to the camera 940 and (ii) to propagate light from the imageprojector 930 to the eye 210 to form image content therein. Using thesame waveguide 940 may simplify the system and/or the eyepiece and maymake the system and/or eyepiece more compact possibly providing areduced form factor. Reducing the thickness of the eyepiece 950 byreducing the number of waveguide 940 may be advantageous for otherreasons as well. Lower cost and a more simplified manufacturing processmay be some such advantages.

Also in various designs, the same or different imaging system may beused in the same head mounted display to image the eye by propagatinglight from the eye via a waveguide in the eyepiece 950 to the camera 940such as, for example, described above. Such systems may also use theeyepiece to transfer light from an illumination source to the eye 210 toilluminate the eye. In some designs, the eyepiece may additionally beused to propagate light from the image projector 930 to the eye 210 toform image content therein. Using the eyepiece to assist in imaging theenvironment and image the eye (and possibly to illuminate the eye) maysimplify the system and/or may make the system more compact possiblyproviding a reduced form factor.

Moreover, in some implementations, the same waveguide 940 may be used to(i) propagate light from the environment in front of the eyepiece 950 tothe camera 940 and (ii) to propagate light from the eye 210 to thecamera to capture images of the eye. The same waveguide may be used topropagate light from the image projector 930 to the eye 210 to formimage content therein and/or to propagate light from the illuminationsource 960 to the eye 210 to illuminate the eye for image capture. Usingthe same waveguide 940 may simplify the system and/or the eyepiece andmay make the system and/or eyepiece more compact possibly providing areduced form factor. Reducing the thickness of the eyepiece 950 byreducing the number of waveguide 940 may be advantage for other reasonsas well. Lower cost and a more simplified manufacturing process may besome such advantages.

Similarly, in addition to coupling light from the environment into thewaveguide 940, the same coupling optical element 944 may be configuredto direct light from the image projector 930 to the eye 210 to formimage content therein and/or light from the eye into the waveguide 940to be guided therein to the camera 920. Additionally or in thealternative, the same coupling optical element 944 may be configured tocouple light from the illumination source 960 guided within thewaveguide 940 out of the waveguide to the user's eye 210.

As discussed above, one or more of the coupling optical element 944, thein-coupling optical element 942, or the out-coupling optical element 952may comprises polarization selective coupling elements. Accordingly, invarious designs, light input into eyepiece 950 or waveguide 940 ispolarized so as to acted on appropriately by the polarization selectiveturning elements.

Accordingly, in some embodiments the illumination source 960 comprises apolarized light source of suitable polarization to be acted on properlyby the polarization selective coupling/turning elements.

One or more polarization specific optical filters and polarizationmodifying elements may be included in various imaging systems 900, suchas those where the image projector 930 and/or light source 960 aredisposed directly opposite each other through the waveguide 940. Thepolarization sensitive elements may be helpful in reducing directionlight emission into the imaging device 920 and/or to reduce saturationof the imaging device 920, for example, in configurations where theseelements are aligned on opposite sides of the waveguide 940 at the samelateral position. FIGS. 15A-15B show such a configuration. The lightsource 960 such as shown in FIG. 15A can be configured to direct lightthrough a polarization specific optical filter 982 such as a polarizer(e.g., a linear polarizer) and/or through a polarization modifyingelement 986 configured to alter a polarization state of incident light,such as a polarization rotator. A retarder such as a half wave retardermay, for example, rotate linear polarization. Accordingly, anappropriately oriented half wave retarder or half wave plate may rotates-polarized light to p-polarized light or vice versa. Accordingly, invarious implementations, the polarization specific optical filter 982and/or a polarization modifying element 986 are disposed in an opticalpath between the light source 960 and the in-coupling optical element942 so as to provide the properly oriented polarization to thein-coupling optical element. In some implementations, the imaging system900 does not include polarization modifying elements but includesproperly oriented polarization optical filters, such as polarizers.

The light emitted by the light source 960 may pass through anarrangement of optical elements in a particular order. For example, asshown in FIG. 15A, the light may pass first from the light source 960through the polarization specific optical filter 982 (e.g., polarizer)and then through the polarization modifying element 986 (e.g. rotator).After the light has passed through the polarization modifying element986, the light may be incident on an incoupling optical element 942,which may direct the light into the waveguide 940 to be guided therein.

For example, the light source 960 may be configured to emit light of amixed polarization (e.g., s-polarization and p-polarization). Thepolarization specific optical filter 982 may be configured to transmitonly light of a first polarization state (e.g., p-polarization). As thelight continues, the polarization modifying element 986 may beconfigured to change the polarization state of the light (e.g., fromp-polarized to s-polarized). The incoupling optical element may beconfigured to turn s-polarized light into an angle that is greater thanthe critical angle of the waveguide such that the s-polarized light isguided within the waveguide. The incoupled light 904 may besubstantially polarized in the second polarization (s-polarization) asit propagates through the waveguide 940. The coupling optical element944 may be configured to turn light only of the second polarizationstate (s-polarization). The coupling optical element 944 may beconfigured to couple the incoupled light 904 out of the waveguide 940and to the eye 210 to provide illumination for image capture.

In order to prevent direct illumination (e.g., saturation) of theimaging device 920, a polarization modifying element 958 and/or apolarization specific optical filter 984 may be disposed in or on thewaveguide 940 such that only light of a certain polarization state(e.g., p-polarized) can pass through the polarization specific opticalfilter 984 and to the imaging device 920. The polarization modifyingelement 958 (e.g., half waveplate) may be configured to change the stateof the polarization (e.g., from s-polarized to p-polarized). Thepolarization specific optical filter 984 may be configured to transmitonly light of a certain polarization (e.g., p-polarized light)therethrough. In this way, light passing through the polarizationspecific optical filter 982 will not be configured to transmit directlythrough the polarization specific optical filter 984. In any of theimplementations above (e.g., where the image projector 930 and/or thelight source 960 are on the same optical axis as shown in FIG. 15A),such as in FIGS. 10, 11A-11E, and 12A-12E, the configuration of thepolarization specific optical filter 982, the polarization modifyingelement 986, the incoupling optical element 942, the polarizationmodifying element 958, and/or the polarization specific optical filter984 may be implemented according to the design of FIG. 15A. Thepolarization specific optical filter 984 may be atransmissive-reflective polarizer (e.g., a polarizer beam splitter)configured to transmit light of a first polarization and to redirect orreflect light of a second polarization different from the first.

A partially reflective element (e.g., semi-transparent mirror) may beincluded to turn the incoupled light 904 to the imaging device 920. Thepartially reflective element may be disposed between the incouplingoptical element 942 and the polarization modifying element 986 such thata portion of the incoupled light 914 is reflected toward the imagingdevice 920 while reducing leakage of the incoupled light 914 out of thewaveguide 940. The portion of light that does not leak out may be anyfraction between 0 and 1. For example, the portion may be 0.90, where90% of the light rays propagating through the waveguide 940 along thecoupling optical element 944 are maintained within the waveguide 940 ateach reflection of the light rays. Other portions are possible (e.g.,0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or any value in a rangebetween these values).

FIG. 15B illustrates propagation of light reflected or scatter off theretina. Some of the light 910 reflected from the retina that is incidenton the coupling optical element 944 having the second polarization(s-polarization) is turned by the coupling optical element 944 at anglegreater than the critical angle of the waveguide 940 and thus may beguided therein. Some of the light may not be coupled into the waveguide940 and will transmit therethrough as non-incoupled light 912. Theincoupled light 904 may propagate through the waveguide 940 toward thecamera.

Other implementations may benefit from use of polarization selectiveelements proximal the light source and camera. For example, varioussystems can be configured to provide illumination having a firstpolarization and capture images with the camera using light having adifferent polarization. For example, such a configuration may be used toreduce unwanted reflections, such as from the cornea when imaging theretina. Reflecton from the cornea will be specular. Accordingly, iflight of a first polarization is incident on the cornea, the lightreflected from the cornea will retain that first polarization. Incontrast, the retina is diffuse. If light of a first polarization isincident on the retina, the light reflected from the retina does notretain solely the first polarization. The diffuse reflection more likelyresults in unpolarized light. Accordingly, a second polarization,different from the first polarization will be present in the reflectedlight. Likewise by illuminating with a first polarization and imagingwith a second different polarization, the retina can be image withreduced glare from the cornea.

Accordingly, in various implementations, the polarization specificoptical filters 982, 984 may be used together to reduce unwantedreflected light from the eye 210 (e.g., from the cornea). For example,unwanted light, glare, or glint may be reflected off the cornea that maysaturate an image captured by the imaging device 920. Light reflectedfrom the cornea may be specular and maintain its polarization. Bycontrast, light reflected off the retina may be more diffusely reflectedand may be less homogenously polarized. Likewise, a combination ofpolarizers may be used to remove some or most of the unwanted reflectedlight. Initially polarized light can be used for illuminating the eye210. In some designs, a polarized illumination source (e.g., the lightsource 960) may be used. Additionally or alternatively, a firstpolarizer (e.g., the polarization specific optical filter 982) may bepositioned at the beginning of the optical path of the illuminationsource to provide initial polarization of the light. A second polarizer(e.g., the polarization specific optical filter 984) may be positionedat the optical path before the light enters the imaging device 920. Thesecond polarizer may be rotated at 90° from the first polarizer (e.g.the polarizers 982, 984 may be “crossed”). As a result, the eye will beilluminated with the first polarization with some light of the firstpolarization reflected from the cornea. This light will not pass throughthe polarizer 984 proximal the camera. However, light reflected from theretina will include the second polarization. Likewise light diffuselyreflected from the retina will pass through the polarize 984 proximalthe camera and will enable an image of the retina to be captured by thecamera. Thus, in such as configuration unwanted light received from theeye (e.g., from cornea) may be entering the imaging device 920 may bereduced or eliminated. Other configurations are possible. For example, apolarization selective incoupling optical element 942 for coupling lightfrom the light source 960 into the waveguide 940 and a polarizationselective outcoupling optical element for coupling light out of thewaveguide to the camera 920 may be employed having differentpolarization selectivity properties. For example, the polarizationselective incoupling optical element may selectively turn light from theillumination source having a first polarization into the waveguide whilethe outcoupling optical element may selectively turn light of a seconddifferent polarization out of the waveguide to the camera. The effectmay again be to reduce or remove unwanted light received from the eye(e.g., from cornea) before entering the imaging device 920.

Various imaging systems 900 are discussed herein that are capable ofusing the eyepiece 950 to collect light to image the retina. The imagingsystems 900, however, can be configured to image other portions of theeye such as anterior portions of the eye. FIG. 16 illustrates how animaging system 900 can be used for imaging an anterior portion (e.g.,cornea) of an eye 210. The imaging system 900 may include one or moreelements of the example imaging systems 900 described above. Inaddition, an example imaging system 900 may include one or more poweredoptical elements or lenses such as powered refractive optical elements980, 990 having optical power. For example, a positive power lens orpositive lens 980 may be disposed on a proximal side (e.g., closer tothe eye 210) of the eyepiece 950 between the eye 210 and the eyepiece. Anegative power lens or negative lens 990 may be disposed on a distalside of the eyepiece 950, between the eyepiece and the environmentforward the user. One or both of the lenses 980, 990 may be variablefocus elements (e.g., varifocal lenses) and/or may include a liquidcrystal element. In some designs, one or both of the lenses 980, 990includes a Fresnel lens. The lenses 980, 990 may incorporate liquidcrystals to produce Fresnel lens functionality. Such functionality mayallow for variable focus of one or both of the lenses 980, 990. In somedesigns, one or more of the lenses 980, 990 may be integrated withand/or manufactured (e.g., formed) on or into the eyepiece 950.

In various embodiments, the coupling optical element 944 is configuredto turn collimated light reflected from the eye 210 into the light guideto be guided therein. Accordingly, the positive lens 980 may beconfigured to collimate light reflected from the eye 210, such as ananterior portion of the eye (e.g., the cornea). The positive lens 980therefore may have a focal length that is equal or substantially equalto the distance of the lens to the portion of the eye 210 to be imaged,e.g., the cornea.

The negative lens 990 may have a similar or the same optical power asthe positive lens 980 to offset or counter the optical power of thepositive lens. In this way, light from the environment (e.g., distal ofthe waveguide 940) may pass through the negative lens 990, the eyepiece950, and the positive lens 980 with substantially no net change inoptical power introduced by these two lenses. Thus, the negative lens990 may be configured to offset or cancel out the optical power of thepositive lens 980 such that a user will not experience the power of thepositive lens when viewing the environment in front of the eyepiece 950.The negative lens 990 will also counter the effect of the positive lens980 to invert images of object in the environment in front of thewearer.

FIG. 16 illustrates light 928 that is incident on the cornea scatteringtherefrom. The imaging system 900 may be configured to capture thislight 988 reflected from the cornea. For example, the positive lens 980may collect a portion of the light 988 scattered from the cornea andcollimate this light 988. This light 988, collimated by the positivelens 980, is incident on the coupling optical element 944, which isconfigured to turn collimated light into the waveguide 940 at an anglelarger than the critical angle of the waveguide such that the light isguided therein by TIR. The coupling optical element 944, the outcouplingoptical element 952, and/or the waveguide 940 may be as described above.Resultant outcoupled light 906 may be directed by the outcouplingoptical element 952 out of the waveguide 940 to the camera (not shown).

FIG. 16 shows light 928, such as collimated light, which may be from theeyepiece 950 such as describe above. An illumination source 960 maycouple light into the waveguide 940 and the coupling element 944 maycouple this light from the illumination source 960 out of the waveguide.The coupling element 944 may be configured to couple light out of thewaveguide 940 as collimated light. This light illuminates the anteriorportion of the eye (e.g., the cornea) and scatters therefrom. Asdiscussed above, this scattered light 988 can be collected by thepositive lens 980 and the imaging system 900 to form an image of theanterior portion of the eye 210. Also as discussed above, thisillumination 928 directed onto the eye 210 may be invisible (e.g.,infrared) light.

FIG. 16 also shows an alternative arrangement for illuminating the eye210. In some designs, one or more light sources 934 such as LEDs oremitters may be disposed with respect to the eye 210 to direct lightthereon without being guided by TIR through the waveguide 940 anddirected onto the eye 210. In some implementations, the eyepiece 950 orwaveguide 940 is not in an optical path between the one or more lightsource 934 and the eye 210. In some designs, a plurality of such lightsources 934 may be arranged in a pattern (e.g., circular or ring-likepattern) near and/or around the eye. In some designs, the pattern oflight sources 934 may define an illumination axis parallel (e.g.,coaxial) with the optical axis of the one or more lenses 980, 990. Theone or more light sources 934 may be similar to the one or more lightsources 960 described above and may, for example, be pulsed. Similarly,the one or more light sources 934 may comprise infrared light sourcessuch as infrared LEDs or another type of invisible light. Alternatively,the one or more light sources may comprise visible light sources thatemit visible light. Or the one or more light sources may emit bothvisible and invisible (e.g., infrared) light.

FIG. 17 illustrates another example imaging system 900 configured toimage a portion of the eye 210 such as an anterior portion of the eye(e.g., cornea). The imaging system 900 shown in FIG. 17 employs areflective optical element 996 configured to collimate the light fromthe eye, in contrast to the transmissive optical element (lens) 980shown in FIG. 16 . A reflective optical element will have lessaberration than a transmissive optical element as chromatic aberrationis not generally applicable to reflective optical elements such as thereflector 996 shown in FIG. 17 . Accordingly, by using a reflectivesurface in collecting light from the eye 210, less (e.g., chromatic)aberration is introduced in the image captured of the eye.

FIG. 17 illustrates, for example, an imaging system 900 that includes acurved transmissive optical element 996 having a wavelength dependentreflective coating 998. The curved transmissive optical element 996 maybe disposed distal the waveguide 940 (on the environment side of theeyepiece 950). Accordingly, the curved transmissive optical element 996may be disposed between the environment forward the wearer and thewaveguide 940 and/or the coupling optical element 944. Similarly, thewaveguide 940 and/or the coupling optical element 944 may be disposedbetween the curved transmissive optical element 996 and the eye 210.

The wavelength dependent reflective coating 998 may be configured toreflect light of a certain wavelength or range of wavelengths. In someimplementations, for example, the wavelength dependent reflectivecoating 998 may be configured to reflect invisible light (e.g., infraredlight) within a certain range of wavelength, while the wavelengthdependent reflective coating 998 may be configured to transmit visiblelight. The wavelength dependent reflective coating 998 may be disposedon a surface of the curved transmissive optical element 996, in somecases.

As discussed above, in various designs, the coupling optical element 944is configured to turn collimated light reflected from the eye 210 intothe waveguide 940 to be guided therein. Accordingly, the reflectiveoptical element 996 may be configured to collimate light reflected fromthe eye 210, such as an anterior portion of the eye (e.g., the cornea).The curved reflective optical element 996 may therefore have a positiveoptical power for light that is incident on the proximal side thereofthat is reflected from wavelength dependent reflective coating 998. Inparticular, in various designs, the reflective optical element 994 mayhave a focal length that is equal or substantially equal to the distancefrom the reflective optical element 996 to the portion of the eye 210 tobe imaged, e.g., the cornea, iris, etc. Example values of focal lengthsmay be, for example, 2 cm to 8 cm. In some implementations, the focallength is between 4 cm and 6 cm. In some designs, the focal length isabout 5 cm. The focal length may be in any range formed by any of thesevalues or may be outside such ranges in different designs.

In various implementations, the reflective optical element 996 isdisposed on the distal side of the eyepiece 950 forward the eyepiece.Accordingly, the reflective optical element 996 is disposed between theeyepiece 950 and the environment forward the user. Similarly, theeyepiece 950 is disposed between the reflective optical element 996 andthe eye 210.

The curved transmissive optical element 996 may have a curved reflectivesurface having a curvature of any shape. In some implementations, thesurface is rotationally symmetric. In some implementations, the surfacemay be spherical or aspheric (e.g., parabolic). Non-rotationallysymmetric shapes are also possible. In various designs, however, thereflective surface has positive optical power. The reflective opticalelement 996 may comprise, for example, a concave mirror at least forsome wavelengths and/or polarizations.

The curved transmissive optical element 996 may be configured to havenegligible power in transmission. Likewise, the curved transmissiveoptical element 996 may be configured to transmit light withoutintroducing convergence or divergence. In one example, the curvedtransmissive optical element 996 may have a curvature of an inner radiussubstantially the same as a curvature of an outer radius. A thin opticalelment 996 may reduce optical aberration, for example, for lighttransmitted therethrough, may be lighter and/or may be more compact.

In various designs, the reflective optical element 996 comprisesmaterial transmissive to visible light such that the user can see theenvironment in front of wearer. In some cases, to enhance transmission,the curved transmissive optical element 996 may be coated on an outersurface (e.g., the distal surface) with an anti-reflective coating. Theanti-reflective coating may be configured to reduce reflection of, forexample, of visible light such as red, green, and/or blue light. Thereflective optical element 996, however, may be configured to reflect aportion of the light scattered from the eye 210 to form an image of theeye. Accordingly, the reflective optical element 996 may operate ondifferent light differently. For example, the reflective optical element996 may operate on different wavelengths differently. The reflectiveoptical element 996 may be configured to reflect infrared light andtransmit visible light.

As discussed above, one or more light sources 934 may be configured toilluminate the eye 210 with infrared light. Resultant light 988reflected from the eye 210 (e.g., cornea) may be diverge, asschematically illustrated in FIG. 17 . The curved transmissive opticalelement 996 may be disposed to receive this light 988 reflected from theeye (e.g., cornea, iris). The wavelength dependent reflective coating998 may be configured to reflect the light 988 reflected from the eyebecause the wavelength illumination used to illuminate the eye is thesame wavelength that is reflected by the reflective coating on thecurved transmissive optical element 996 (e.g., 850 nm). For example theeye may be illuminated with infrared light (e.g., 850 nm) and the curvedtransmissive optical element 996 may be configured to reflect infraredlight (e.g., 850 nm) and to pass visible light. The shape of the curvedtransmissive optical element 996 may also be configured to collimate thelight 988 reflected from the eye and to reflect the light to thecoupling optical element 944, which turns the collimated light into thewaveguide 940 to be guided therein by TIR.

In FIG. 17 , as in some other designs, one or more light sources 934such as LEDs or emitters may be disposed with respect to the eye 210 todirect light thereon without being guided by TIR through the waveguide940 and directed onto the eye 210. In some implementations, the eyepiece950 or waveguide 940 is not in an optical path between the one or morelight source 934 and the eye 210. In some designs, a plurality of suchlight sources 934 may be arranged in a pattern (e.g., circular orring-like pattern) near and/or around the eye. In some designs, thepattern of light sources 934 may define an illumination axis parallel(e.g., coaxial) with the optical axis of the one or more lenses 980,990. The one or more light sources 934 may be similar to the one or morelight sources 960 described above and may, for example, be pulsed.Similarly, the one or more light sources 934 may comprise infrared lightsources such as infrared LEDs or another type of invisible light. Othertypes of light sources, however, can be used.

FIG. 18 illustrates another example imaging system 900 configured toimage a portion of the eye 210 such as an anterior portion of the eye(e.g., cornea). In the implementation shown in FIG. 18 , polarizationselectivity is employed to assist in controlling the path of the lightreflected from the eye. In particular, in various designs, the couplingoptical element 944 is polarization selective. Light, for example,having a first polarization is transmitted through the coupling opticalelement 944 while light of a second different polarization is turned bythe coupling optical element 944 into the waveguide 940 to be coupledtherein by TIR. Accordingly, in various implementations the eye 210 isilluminated with polarized light or a polarizer (not shown) is disposedbetween the eye and the waveguide 940 such that the light from the eyeincident on the waveguide is polarized. For example, the emitters 934may emit polarized light or a polarizer may be disposed in front of theemitters 934 such that the eye 210 is illuminated with polarized light.Accordingly, in various designs, the polarization of the polarized lightincident and/or reflected from the eye 210 that is received by theoptical coupling element 944 may the first polarization such that saidlight is directed to the reflector 996.

Likewise, in various implementations, the coupling optical element 944(and/or an outcoupling optical element 952) is configured to transmitlight of a first polarization state such as a first linear, circular, orelliptical polarization state (e.g., p-polarization, left handedcircular or elliptical polarization, etc.) and turn light of a secondpolarization state such as a second linear, circular, or elliptical(e.g., s-polarization, right handed circular or elliptical polarization,etc.) into and/or out of the waveguide, respectively. In someimplementations, the eye illuminators 934 may emit only or primarily thefirst polarization (e.g., p polarization) or further include apolarization modifying element (e.g., polarizer) that is configured totransmit only light of the first polarization state (e.g.,p-polarization). Additionally, the coupling optical element 944 and/oroutcoupling optical element 952 may be configured to turn light of asecond polarization (e.g., s-polarization) into and/or out of thewaveguide, respectively.

Similar to the imaging system 900 shown in FIG. 17 , an imaging system900 the curved reflector 998 shown in FIG. 17 comprises a curvedtransmissive optical element 996 having a wavelength dependentreflective coating 998. The wavelength dependent reflective coating 998may be configured to reflect light of a certain wavelength or range ofwavelengths. In some implementations, for example, the wavelengthdependent reflective coating 998 may be configured to reflect invisiblelight (e.g., infrared light) within a certain range of wavelength, whilethe wavelength dependent reflective coating 998 may be configured totransmit visible light. The wavelength dependent reflective coating 998may be disposed on a surface of the curved transmissive optical element996, in some cases.

In various implementations, the curved transmissive optical element 996is disposed on the distal side of the eyepiece 950 forward the eyepiece.Accordingly, the reflective optical element 996 is disposed between theeyepiece 950 and the environment forward the user. Similarly, theeyepiece 950 is disposed between the reflective optical element 996 andthe eye 210.

Accordingly, light having the first polarization (e.g., p-polarization)from the eye 210 is incident on the coupling optical element 944 andpasses therethrough to the curved transmissive optical element 996. Theimaging system 900 further included a polarization modifying opticalelement 978, such as a retarder (e.g., a quarter-wave retarder). Thisretarder 978 is transmissive and imparts a quarter wave of retardance onthe light transmitted therethrough. This light is incident on andreflected from the curved transmissive optical element 996. Thewavelength dependent reflective coating 998 may be configured to reflectthe wavelength of light reflected from the eye. Consequently, this lightis reflected from the curved surface of the curved transmissive opticalelement 996 and is collimated. This collimated light passes againthrough the retarder 978, thereby imparting another quarter wave ofretardance on the light transmitted therethrough. The retardanceintroduced on these two passes through the retarder (e.g., a full waveof retardance) causes the polarization to rotate. Accordingly, the firstpolarization (e.g., p-polarization) transmitted through the polarizationselective coupling optical element 944 on the first pass, is transformedinto the second polarization (s-polarization) and is turned into thewaveguide 940 to be guided to the camera 920 by TIR. As discussed above,in various designs, the coupling optical element 944 is configured toturn collimated light reflected from the eye 210 into the waveguide 940to be guided therein. Accordingly, the reflective optical element 996may be configured to collimate light reflected from the eye 210, such asan anterior portion of the eye (e.g., the cornea). The curved reflectiveoptical element 996 may therefore have a positive optical power. Inparticular, in various designs, the reflective optical element 994 mayhave a focal length that is equal or substantially equal to the distancefrom the reflective optical element 996 to the portion of the eye 210 tobe imaged, e.g., the cornea, iris, etc. Example values of focal lengthsmay be for example, 2 cm to 8 cm. In some implementations, the focallength is between 4 cm and 6 cm. In some designs, the focal length isabout 5 cm.

In various designs, the reflective optical element 996 may comprise acurved surface that is configured to reflect light. The curved surfacemay be spherical or rotationally symmetric in certain cases. Thereflective optical element 996 may comprise, for example, a concavemirror at least for some wavelengths and/or polarizations.

In various designs, the reflective optical element 996 comprisesmaterial transmissive to visible light such that the user can see theenvironment in front of wearer. The wavelength dependent reflectivecoating 998 disposed on a surface of the curved transmissive opticalelement 996 may therefore be transmissive to visible light or at leastcertain wavelength of visible light. The curved transmissive opticalelement 996 may also be coated on an outer surface (e.g., the distalsurface) with an anti-reflective coating. The anti-reflective coatingmay be configured to reduce reflection of red, green, and/or blue light.The reflective optical element 994, however, may be configured toreflect a portion of the light scattered from the eye 210 to form animage of the eye. Accordingly, the reflective optical element 996 mayoperate on different light differently. For example, the reflectiveoptical element 996 may operate on different polarization states (and/orwavelengths) of light differently. The reflective optical element 996may be configured to transmit visible light and reflect infrared light.

As shown in FIG. 17 , the one or more light sources 934 such as LEDs oremitters in FIG. 18 may be disposed with respect to the eye 210 todirect light thereon without being guided by TIR through the waveguide940 and directed onto the eye 210. Accordingly, n some implementations,the eyepiece 950 or waveguide 940 is not in an optical path between theone or more light sources 934 and the eye 210. In some designs, aplurality of such light sources 934 may be arranged in a pattern (e.g.,circular or ring-like pattern) near and/or around the eye. The one ormore light sources 934 may be similar to the one or more light sources960 described above and may, for example, be pulsed. Similarly, the oneor more light sources 934 may comprise infrared light sources such asinfrared LEDs or another type of invisible light. In particular, invarious implementations the light sources 934 may emit light that isreflected by the wavelength dependent reflective coating 998 and/or thecurved transmissive optical element 996. Other types of light sources,however, can be used.

Although the polarization selective coupling optical element 944 isconfigured to be polarization selective depending on the type of linearpolarization incident thereon, other polarization selective couplingoptical elements may be polarization selective to other types ofpolarization states such as different types of circular or ellipticalpolarization. The polarization selective coupling optical element 944may, for example, be configured such that the first polarization, suchas a first circular or elliptical polarization (e.g., left handedpolarization or LHP-polarization), is transmitted through thepolarization selective coupling optical element 944 and the secondpolarization, such as second circular or elliptical polarization (e.g.,right handed polarization or RHP), is turned into the light guide, orvice versa. Such a polarization selective coupling optical element 944may comprise liquid crystal such as cholesteric liquid crystal. Examplesof some liquid crystal optical elements are discussed below in thesection titled “Cholesteric Liquid Crystal Mirror,” in U.S. PublicationNo. 2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERICLIQUID CRYSTAL,” filed on Dec. 7, 2017; in U.S. Publication No.2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWER REFLECTOR,”filed on Feb. 22, 2018; in U.S. Publication No. 2018/0239177, titled“VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATION CONVERSION,”filed on Feb. 22, 2018; each of which is hereby incorporated byreference in its entirety and for all purposes.

A polarization modification element or retarder such as a circularpolarizer may be disposed between the eye and the polarization selectivecoupling optical element 944 to convert the light reflected from the eyeto the first polarization (e.g., LHP). The LHP light will pass throughthe polarization selective coupling optical element 944, reflect fromthe reflector 998, change polarization into RHP and be turned by thepolarization selective coupling optical element 944 into the waveguideto the camera.

In some implementations, the reflector 996 may be polarization selectivein its reflectivity such that only light of a certain polarization stateis reflected and/or that light of a different polarization state istransmitted. Such an optical element may comprise liquid crystal such ascholesteric liquid crystal. Examples of such optical elements arediscussed below in the section titled “Cholesteric Liquid CrystalMirror,” in U.S. Publication No. 2018/0164627, titled “DIFFRACTIVEDEVICES BASED ON CHOLESTERIC LIQUID CRYSTAL,” filed on Dec. 7, 2017; inU.S. Publication No. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLEPOWER REFLECTOR,” filed on Feb. 22, 2018; in U.S. Publication No.2018/0239177, titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ONPOLARIZATION CONVERSION,” filed on Feb. 22, 2018; each of which ishereby incorporated by reference in its entirety and for all purposes.Such optical elements may reflect light of a first polarization statesuch as a first circular or elliptical polarization state (left handedcircular or elliptical polarization) and transmit light of a secondpolarization state such as a second circular or elliptical polarizationstate (e.g. right handed circular or elliptical polarization) or viceversa. In some embodiments, the liquid crystal is disposed on a curvedsurface of the reflector 996 such that in reflection, the reflector hasoptical power such as positive optical power. In various otherimplementations, the liquid crystal optical element may be flat orplanar. For example, the liquid crystal may be disposed on a flat orplanar substrate or layer. Despite being flat, optical power may beincluded in the liquid crystal optical element. Such an element may bereferred to as a cholesteric liquid crystal reflective lens.Accordingly, light from the eye may be collimated and reflected to thecoupling optical element 998. The reflector, for example, may reflectlight of a first polarization state (e.g., left handed circular orelliptical) and transmit light of a second polarization (e.g., righthanded circular or elliptical polarization). Accordingly, the eye 210 isilluminated with left handed circular polarized light or the lightreflected from the eye is transmitted through a polarizer (e.g., acircular or elliptical polarizer) that transmits light having the firstpolarization (e.g., left handed circular or elliptical polarized light).The coupling optical element 944 may also be polarization selective andmay transmit LHP light and turn RHP light into the waveguide. The LHPlight from the eye passes through the coupling optical element 944. Thistransmitted LHP light also is incident on the wavelength-selectiveliquid crystal reflector 996 and reflected therefrom. In certaindesigns, the wavelength-selective liquid crystal reflector 996transforms the first polarization state (e.g. LHP) into the secondpolarization state (e.g. RHP) upon reflection. This light of the secondpolarization state (e.g., RHP light) is directed to the coupling opticalelement 944, which turns light of the second polarization state (RHP)into the waveguide 940 to the camera 920.

In some designs, the coupling optical element 944 does not comprise aliquid crystal grating but instead comprises, for example a surfacerelief diffraction grating or holographic grating. As discussed above,these coupling optical element 944 that do not comprise cholestericliquid crystal may also comprise a volume diffractive or holographicoptical elements or grating.

Accordingly, light scattered from the eye, is reflected by thereflective optical element 996 back to the waveguide 940 for couplinginto the waveguide by the coupling element 944. In contrast, however, aportion of the unpolarized light from the environment in front of thewearer corresponding to the second polarization state (e.g., RHP) wouldbe transmitted through the reflective optical element 996. Thus, thewearer could see objects through the reflective optical element 996.

In various designs, however, the reflective optical element 996 wouldhave negligible power in transmission. For example, the reflectiveoptical element 996 may have curved surfaces on both sides of theoptical element having the same curvature such that the aggregate powerof the optical element for light transmitted therethrough would benegligible.

As discussed above, in various implementations, the reflective opticalelement 996 comprises a cholesteric liquid crystal reflective lens, acholesteric liquid crystal reflective element such as discussed below inthe section titled “Cholesteric Liquid Crystal Mirror,” in U.S.Publication No. 2018/0164627, titled “DIFFRACTIVE DEVICES BASED ONCHOLESTERIC LIQUID CRYSTAL,” filed on Dec. 7, 2017; in U.S. PublicationNo. 2018/0239147, titled “DISPLAY SYSTEM WITH VARIABLE POWER REFLECTOR,”filed on Feb. 22, 2018; in U.S. Publication No. 2018/0239177, titled“VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATION CONVERSION,”filed on Feb. 22, 2018; each of which is hereby incorporated byreference in its entirety and for all purposes. Such optical element mayoperate on a particular wavelength or wavelength range. Accordingly,light such as infrared light reflected from the eye may be acted on bythe cholesteric liquid crystal reflective element. However, light not inthat wavelength range such as visible light from the environment may bepassed through the cholesteric liquid crystal reflective element withoutbeing operated on by the cholesteric liquid crystal reflective element.Accordingly, the cholesteric liquid crystal reflective element may havenegligible power for this visible light from the environment passingtherethrough.

As discussed above, in certain implementations, the illumination source960 couples light into the waveguide 940 that is turned out of thewaveguide to illuminate the eye 210. In such embodiments, the couplingoptical element 944 may be polarization selective. For example, thecoupling optical element 944 may transmit a first polarization(p-polarization) and transmit a second polarization (s-polarization).

Accordingly, if light from the illumination source 906 propagatesthrough the waveguide 940 and is turned by the coupling optical element944, this illumination will be s-polarization. A polarization modifyingoptical element (e.g., a quarter wave retarder) may be disposed betweenthe waveguide 940 and the eye 210 so as to cause rotation of thepolarized light reflected from the eye. Light from the light source 960that is reflected from the eye 210 will pass twice through the quarterwave retarder and as a result the s-polarized light ejected from thewaveguide by the coupling element 944 to illuminate the eye will betransformed into p-polarized light.

This p-polarized light will be transmitted through the coupling opticalelement 944 and the waveguide and be incident on the reflective opticalelement 996.

The imaging system 900 may further comprise a second polarizationmodifying element 978 which may comprise, for example, a retarder orwaveplate as discussed above. This retarder may comprise for example aquarter wave retarder. The second polarization modifying element 978 maybe disposed distal of the waveguide 940, between the waveguide and thereflector 996. The second polarization modifying element 978 may also bedisposed between the coupling element light 944 and the reflector 996.Light (p-polarized) from the eye 210 that is transmitted through thecoupling element light 944 passes through second polarization modifyingelement 978 is transformed into circular polarization. If the reflector996 reflects circular polarized light, this light will be reflected backto the waveguide 940 after passing again through the polarizationmodifying element 978. Two passes through this polarization modifyingelement (e.g., quarter wave retarder) 978 will cause the light to betransformed into s-polarized light, which will be turned by the couplingelement 944 into the waveguide to be guide therein to the camera (notshown).

As illustrated in FIG. 18 , the light 988 reflected from the eye 210 isdiverging. This light is incident on the reflector 996, which is curvedor otherwise has positive optical power, and may be collimated thereby.The coupling optical element 944, which is configured to turn collimatedinto the waveguide 940, will therefore direct this collimated light fromthe curved reflective optical element 996 toward the imaging device 920(not shown). Accordingly, the light reflected from the eye 210 that iscollimated by the curved reflective optical element 996 is coupled intothe waveguide 940 and guided therein toward the outcoupling opticalelement 952. The outcoupling optical element 952 may be configured todirect the light out of the eyepiece 950 to the camera (not shown).

A wide variety of variations are possible in the configurations of theimaging system. Different types of reflectors 996 and coupling elements944 may be employed. The reflectors 996 and coupling elements 944 may,for example, be configured to operate on linear polarized light orcircular or elliptical polarized light. As discussed, the reflectors 996have optical power. The reflectors 996 and coupling elements 944 maycomprise cholesteric liquid crystal grating reflectors and/or lenseswith our without optical power. Polarization modifying elements 978 suchas retarders may be included between the coupling elements 944 and thereflector and/or between the coupling elements 944 and the eye. In someembodiments, a polarizer such as a circular polarizer or a linearpolarizer may be disposed between the eye and the coupling elements 944.If for example unpolarized light is reflected from the eye, a polarizer(e.g., circular polarizer or linear polarizer) may be disposed betweenthe eye and the coupling elements 944. In some such cases the couplingelements 944 are polarization selective.

In configurations such as shown in FIGS. 17 and 18 , where lightreflected from the eye passes through the waveguide 940 to the curvedreflective optical element 996 to be collimated and redirected back tothe waveguide, background noise is introduced. This background noiseresults from light passing initially from the eye through the couplingoptical element 944. As discussed above, the coupling optical element944 may be configured to turn collimated light into the waveguide 940 tobe guided therein to the camera 920 where an image is formed. Thecoupling optical element 944 will, however, turn some non-collimatedlight incident thereon. Accordingly, on the initial pass through thecoupling optical element 944 and the waveguide 940 to the curvedreflective optical element 996, some of the non-collimated (diverging)light reflected from the eye will be coupled by the coupling opticalelement 944 into the waveguide and contribute background noise to imageof the eye formed at by the camera 920. This noise will be superimposedon the image formed by the collimated light retro-reflected by thecurved reflective optical element 996 that is coupled by the couplingoptical element 944 into the waveguide to be guided therein to thecamera 920.

In certain designs, this noise can be subtracted out from the image. Theprocess for subtracting out the noise from the signal may involve (a)measuring the amount of light coupled by the coupling optical element944 on the initial pass through the coupling optical element 944 to thecurved reflective optical element 996 that is turned and reaches thecamera 920 (referred to as N) and (b) measuring the total signal at thecamera 920 when light passes through coupling optical element 944 andthe waveguide 940 to the curved reflective optical element 996, iscollimated, and reflected back to the coupling optical element andturned to the camera. This total signal will also include some noise, N,as the uncollimated light reflected from the eye will have passedthrough the coupling optical element 944 to get to the curved reflectiveoptical element 996 and thus some of uncollimated light will be turnedby the coupling optical element 944 to the camera 920. If the noise, N,can be measured separately from the total signal, T, that includes thenoise superimposed over the image of the eye, the noise, N, can besubtracted out from the total signal, T, as represented by the formulabelow:

I=T−N

where I represents the image with the noise component, N, removed.

The two measurements (a) and (b) above can be obtained in various ways.For example, as shown in FIG. 19 , a shutter 936 can be disposed betweenthe curved reflective optical element 996 and the waveguide 940 andcoupling optical element 944. This shutter 936 may be configured toblock light when the shutter is in a first state and to transmit lightwhen the shutter is in a second state. This shutter 936 may comprise,for example, a liquid crystal shutter.

Accordingly, the noise component N can be measured when the shutter 936is in the first state where light reflected from the eye 210 is incidenton the coupling optical element 944, passes therethrough toward thecurved reflective optical element 996, however, is prevented fromreaching the curved reflective optical element by the closed shutter. Asdiscussed above, some of the light reflected from the eye 210, althoughmainly uncollimated, does couple into the coupling optical element 944and is turned into the waveguide and guided therein to the camera 920.As referenced above, this light does not contribute to formation of animage, but will be background noise. The camera 920 may record thisnoise, N, when the shutter 936 is closed.

The total signal, T, including both the noise, N, and the image, can bemeasured when the shutter 936 is in the second state where the shutteris open. Light reflected from the eye 210 is again incident on thecoupling optical element 944. Some of this light reflected from the eye210, although mainly uncollimated, couples into the coupling opticalelement 944 and is turned into the waveguide and guided therein to thecamera 920. Most of this light reflected from the eye 210, however,passes through the coupling optical element 944, through the openshutter 936 and to the curved reflective optical element 996. The curvedreflective optical element 996 collimates and reflects at least aportion of this light back to the coupling optical element 944, whichturns this collimated light into the waveguide 920 to be guided to thecamera 920 to form an image of the eye 210. The camera 920 can capturethis image of the eye 210.

Processing electronics (such as processing electronics 140) incommunication with the camera 920 can receive the noise component, N,measured when the shutter 936 was in the first closed state as well asthe total signal, T, measured when the shutter was in the second openstate and can subtract the two (T−N). In this manner, the noise, N,contributed by the non-collimated light reflected from the eye 210 thatis coupled into the coupling optical element 944 on the initial passtherethrough, can be subtracted from the total image signal, T. Theprocessing electronics may be in communication with the camera 920 via awired electronic signal. Additionally or alternatively, the processingelectronics may communicate with the camera 920 using one or more remotereceivers. The processing electronics may reside remotely (e.g., cloudcomputing devices, remote server, etc.).

Other ways may be employed to perform the measurement of (a) and (b) toobtain N and T and subtract N from T. For example, if the curvedreflective optical element 996 is wavelength selective such as shown inFIG. 18 , the eye can be illuminated with light of different wavelengthat different times. For example, to perform the measurement (a) andquantify the noise, N, the eye can be illuminated with a wavelength thatis not reflected by the curved reflective optical element 996. However,to perform the measurement (b) and quantify the total signal, T, the eyecan be illuminated with a wavelength that is reflected by the curvedreflective optical element 996. The noise, N, can then be subtractedfrom the total T, as discussed above (e.g., T−N).

FIGS. 20-20E illustrate an example imaging system 900 configured to usewavelength modulation to measure and subtract out the noise component,N, as discussed above. The imaging system 900 in FIGS. 20A-20E includesa curved transmissive optical element 996 that is wavelength selective(such as described with reference to FIGS. 17 and 18 above). Forexample, the curved transmissive optical element 996 has a wavelengthdependent reflective coating 998 on a curved surface thereof. Theimaging system 900 may also include one or more light sources orillumination sources (not shown) configured to illuminate the eye 210.The one or more light sources may be configured to emit infrared light.The one or more light sources, however, can be configured to emitdifferent color or wavelength light at different times. Such wavelengthmodulation can enable the measurement of N separately so as to besubtracted out from the total signal, T.

In various implementations, for example, the one or more illuminationsources 960, 934 may be configured in a first state to emit one or morewavelengths that are reflected by the curved reflective optical element,λ_(Reflect), and in a second state one or more wavelengths that are notreflected λ_(Not Reflect). In the second state, no more than negligibleamounts of wavelengths that are reflected by the curved reflectiveoptical element, λ_(Reflect), are emitted. Similarly, in the firststate, no more than negligible amounts of wavelengths that are notreflected λ_(Not Reflect) are emitted.

In some examples, the reflected wavelength(s), λ_(Reflect), may bebetween about 800 nm and 950 nm. The reflected wavelength(s),λ_(Reflect), may be between about 835 nm and 915 nm. The reflectedwavelength(s), λ_(Reflect), may be between about 840 nm and 870 nm. Insome designs, the reflected wavelength, λ_(Reflect), is about 850 nm.The light emission 928 from the one or more light sources 960 mayilluminate the eye.

As shown in FIG. 20B, light 988 having the wavelength(s) that are notreflected by the curved reflective optical element 944, λ_(Not Reflect),(and no more than negligible amounts of light that is reflected by thecurved reflective optical element 944, λ_(Reflect)) is reflected offpart of the eye 210 (e.g., the cornea). Because this light compriseswavelength(s) that are not reflected by the curved reflective opticalelement 944, λ_(Not Reflect), rays of light 916 are shown propagatingthrough the curved reflective optical element 996 to the environmentforward the user.

Although the light 988 incident on the coupling optical element 944 isnot collimated, the coupling optical element nevertheless couples atleast some light 914 into the waveguide 940 to be guided to the camera920. According, the camera 920 may capture an image (Image #1)corresponding to the noise component, N, that results from uncollimatedlight that is turned by the coupling optical element 944 on the initialpass to the curved reflective optical element 996. This image (Image #1)is background noise and does is not a recognizable image of the eye.Processing electronics 140 is shown as receiving this first image (Image#1).

In FIGS. 20C-20E, the illumination sources (not shown) emit one or morewavelengths that are reflected by the curved reflective optical element,λ_(Reflect), and no more than negligible amounts of wavelengths that arenot reflected λ_(Not Reflect). This wavelength, λ_(Reflect), may be, forexample, 850 nm.

As shown in FIG. 20C, some of the light 988 reflected from the eye 210that is incident on coupling optical element 944 in the first passthrough the coupling optical element 944 is coupled by the couplingoptical element 944 into the waveguide 940 (as in FIG. 20B) and directedtoward the camera 920. Additionally, the curved transmissive opticalelement 996, which selectively reflect light of wavelength λ_(Reflect),reflects and collimates the non-incoupled light 918 reflected from theeye 210 that is incident on the curved transmissive optical element. Asillustrated in FIG. 20E, the coupling optical element 944 turns andcouples this collimated reflected light into the waveguide 940 towardthe camera 920. FIG. 20E shows both components reaching the camera 920,light 988 reflected from the eye 210 that is incident on couplingoptical element 944 in the first pass through the coupling opticalelement 944 is coupled by the coupling optical element into thewaveguide 940 and light reflected and collimate by the curvedtransmissive optical element 996 that is coupled by the coupling opticalelement into the waveguide. The camera 920 may capture an image (Image#2) corresponding to this total image component, T. Processingelectronics 140 is shown as receiving this second image (Image #2).

As discussed above, the processing electronics may subtract the noisefrom the image, T−N. In this example, Image #1 can be subtracted fromImage #2. Accordingly, the processing electronics 140 may be configuredto modify the second image based on the first image. Other approaches,however, are possible. For example, the processing electronics 140 maybe configured to create a new image that represents a version of thesecond image with reduced optical noise. Implementations for subtractingnoise from the image may be used in implementations described above. Forexample, implementations shown in FIGS. 10, 11A-11E, and/or FIGS.12A-12E can include a shutter 936 and/or a curved transmissive opticalelement 996 having a wavelength dependent reflective coating 998configured to selectively reflect non-incoupled light 912 and to directthe light to an imaging device 920.

As discussed above, the Image #1 was obtained for the case where thelight was illuminated with one or more wavelengths that are notreflected by the curved reflective optical element, λ_(Not Reflect), andno more than negligible amounts of wavelengths that are reflectedλ_(Reflect) Image #2 was obtained for the case where the light wasilluminated with one or more wavelengths that are reflected by thecurved reflective optical element, λ_(Reflect), and no more thannegligible amounts of wavelengths that are not reflectedλ_(Not Reflect). Accordingly, the one or more illumination sources 960,934 may be configured to modulate in wavelength. For example, in certaindesigns the one or more illumination sources 960, 934 may comprise afirst illumination source configured to output one or more wavelengthsnot reflected by the curved reflective optical element, λ_(Not Reflect),and no more than negligible amounts of wavelengths that are reflectedλ_(Reflect). The one or more illumination sources may further comprise asecond illumination source configured to output one or more wavelengthsthat are reflected by the curved reflective optical element,λ_(Reflect), and no more than negligible amounts of wavelengths that arenot reflected λ_(Not Reflect). The intensity of the first and secondillumination sources can be alternately increased and decreased, turnedon and off, attenuated and not attenuated, passed and blocked to providemodulation in the wavelength of light illuminating the eye. For example,during a first time interval the first illumination source can beblocked while the second illumination source is not blocked. During asubsequent second time interval, the second illumination source can beblocked while the first illumination source is not blocked. This processcan be repeated to provide modulation of the wavelength of lightilluminating the eye. In other designs, the wavelength of a light sourcemay be tuned and detuned to shifted the wavelength back and forthbetween λ_(Reflect) and λ_(Not Reflect). Other arrangements arepossible.

As described above, imaging systems 900 may be included in head mounteddisplays such as augmented reality displays that additionally providethe ability to image the eye by collecting light with the eyepiece 950.Such imaging systems 900 may be used for eye tracking. Multiple imagesof the retina or an anterior portion of the eye may be obtained.Movement and/or repositioning of the eye can be ascertained from theseimages to track the eye position and/or orientation. These imagingsystem may also be use as for biometric imaging and/or for identifyingthe user. For example, an image of the user's eye such as of the retinaor iris may be obtained and recorded. A subsequent image of the eye(e.g., retina, or iris) of the wearer may be obtained at a later time.The two images may be compared to determine whether the wearer in thatlater instance was the wearer in the first instance. Other uses for theimaging systems however are possible.

Although illumination systems may be described above as waveguide basedand comprising one or more waveguides, other types of light turningoptical elements may be employed instead of a waveguide. Such lightturning optical elements may include turning features to eject the lightout of the light turning optical element, for example, onto the spatiallight modulator. Accordingly, in any of the examples described herein aswell as any of the examples below, any reference to waveguide may bereplaced with light turning optical element instead of a waveguide. Sucha light turning optical element may comprise, for example, a polarizingbeam splitter such as a polarizing beam splitting prism.

As discussed above the systems described herein can allow for collectionof biometric data and/or biometric identification. For example, the eyeor portions thereof (e.g., the retina) can be imaged to provide suchbiometric data and/or biometric identification. Images of the eye suchas of the retina may be obtained at various times when the head mounteddisplay system is being worn by a user, presumably the same user. Acollection of such images can be recorded, for example, in a database.These images may be analyzed to collect biometric data. Such biometricdata may be useful for monitoring the user's health or medical status.Different medical parameters can be monitored by imaging the patient,for example, the patient eye (e.g., retina). The medical parameters canbe recorded and compared with subsequent measurements obtained when theuser is wearing the head mounted display system.

In addition, if a person begins wearing the head mounted display systemand an image of the user's eye is captured that does not match theimages stored in the database a conclusion may be drawn that the personcurrently wearing the head mounted display system is different from theprevious user. This can be useful in determining whether the intendeduser is wearing the headset or if it is being worn by a new user. Such afeature may allow for certain medical, security, and/orconvenience-in-use applications or functionality. For example, the headmounted display may be configured to identify a wearer based oncharacteristics of the wearer's eye. For example, the system can beconfigured to determine an individual based on features of a wearer'sretina (e.g. blood vessels), cornea, or other eye features. In someimplementations for example, a series of markers may be determined for aparticular wearer. Based on the series of markers, the system may beable to determine that the previous user is wearing the headset or,alternatively, that another user is wearing the headset. The markers mayinclude a shape or center of a user's cornea, a configuration of bloodvessels in the user's retina, an intensity and/or position of areflection of light from the cornea, a shape of an aspect of the eye,and/or any other biometric marker. In certain implementations aconfusion matrix can be determined. As discussed above for example inthe discussion of developing a retinal map using a virtual/fixationtarget at a variety of location (see, e.g., FIG. 13B), the system mayhave a user look in a set of pre-determined directions or eye poses anddevelop a matrix of characteristics of the eye or part of the eye (e.g.,cornea, retina, etc.) associated with each direction or eye pose. Usingsuch a matrix, the system can determine an identity of the individual.Other methods are possible.

Similarly, as discussed above, a wide variety of configurations of thesystem are possible. For example, FIG. 21 shows an example eyepiece 900that can be used to simultaneously project light into a user's eye whileimaging the user's eye. The eyepiece 900 shown includes an incouplingoptical element 2104, a light distributing element 2108, and a lightconsolidating element 2116, and an outcoupling optical element 2120 onopposite sides of a coupling optical element 2112. Each of these opticalelements may be disposed within or on a waveguide 2102. The waveguide2102 may correspond, for example, to one of the waveguides 670, 680, 690described herein (see, e.g., FIG. 9A-9C). The incoupling optical element2104 may correspond to one of incoupling optical elements 700, 710, 720described herein and/or to the incoupling optical element 942 (see,e.g., FIG. 10 ) and may be configured to inject image content from aprojector into the waveguide and/or illumination from a light source960. The light distributing element 2108 may correspond to one of thelight distributing elements 730, 740, 750 described herein (see, e.g.,FIGS. 9A-9C and may be used to spread light in a given direction andredirect the light from the incoupling optical element 2104 to thecoupling optical element 2112. The coupling optical element 2112 maycorrespond to the coupling optical element 944 described herein (see,e.g., FIG. 10 ). In some designs, the coupling optical element 2112includes functionality described herein with respect to the outcouplingoptical elements 800, 810, 820 (see FIGS. 9A-9C). The lightconsolidating element 2116 may be configured to reduce the lateralspatial extent of light received from the coupling optical element 2112and redirect said light toward the outcoupling optical element 2120. Theoutcoupling optical element 2120 may correspond to the outcouplingoptical element 952 described herein (see, e.g., FIG. 10 ).

The incoupling optical element 2104 may be disposed within or on thewaveguide 2102 so as to receive light, such as from a projector (e.g.,the image projector 930) and/or an illuminator (e.g., the light source960). The light may be passed via the waveguide 2102 to the associatedlight distributing optical element 2108. Any of the incoupling opticalelement 2104, light distributed optical element 2108 or coupling opticalelement 2112 may be disposed on a major surface of (e.g., on a top orbottom surface) of the waveguide or within the waveguide. Similarly, anyone or combination of the light consolidating element 2116, and/or theoutcoupling optical element 2120 may be disposed on the major surface(e.g., a top or both major surface) of the waveguide 2102 or within thewaveguide.

The coupling optical element 2112 may receive the light (e.g., via TIR)from the light distributing element 2108 and expand the light to enterthe user's eye. Thus, the coupling optical element 2112 may be disposedin front of a user's eye and project image content therein. Additionallyor alternatively, the coupling optical element 2112 may be configured toprovide illuminating light onto and/or into the user's eye.

Light that is reflected from the eye (e.g., the illumination light fromthe illumination source) may be reflected and captured by the couplingoptical element 2112. Thus, in some embodiments, the coupling opticalelement 2112 can serve to both outcouple light received from the lightdistributing element 2108 and incouple light received from the eye intothe waveguide 2102.

In some embodiments, the coupling optical element 2112 may include oneor more diffractive optical elements (DOEs) such that the couplingoptical element 2112 has dual functionality. A first DOE (e.g., agrating, holographic region) may be configured to outcouple light aswell and a second DOE may be configured to incouple reflected light fromthe eye into the waveguide 2102. In some embodiments, both the first andsecond DOEs are superimposed (e.g., occupy the same or approximately thesame volume) within the waveguide 2102.

Alternatively, in some embodiments, the coupling optical element 2112includes at least two DOEs that are stacked on over or in front of theother. For example, with reference to FIG. 21 , the first DOE of thecoupling optical element 2112 may be disposed over, whereas the seconddiffractive element may be disposed under the first DOE. The order ofeach DOE may be reversed in other implementations.

Cholesteric Liquid Crystal Mirror

Some liquid crystals are in a phase referred to as a chiral phase or acholesteric phase. In a cholesteric phase, the liquid crystals canexhibit a twisting of the molecules along an axis perpendicular to thedirector, where the molecular axis is parallel to the director. Asdescribed herein, a cholesteric liquid crystal (CLC) layer comprises aplurality of liquid crystal molecules in a cholesteric phase that extendin a direction, e.g., a direction perpendicular to the director such asa layer depth direction, and that are successively rotated or twisted ina rotation direction, e.g., clockwise or counterclockwise. The directorsof the liquid crystal molecules in a chiral structure can becharacterized as a helix having a helical pitch (p), which correspondsto a length in the layer depth direction corresponding to a net rotationangle of the liquid crystal molecules of the chiral structures by onefull rotation in the first rotation direction. In other words, thehelical pitch refers to the distance over which the liquid crystalmolecules undergo a full 360° twist. The liquid crystals displayingchirality can also be described as having a twist angle, or a rotationangle (ϕ), which can refer to, for example, the relative azimuthalangular rotation between successive liquid crystal molecules in thelayer normal direction, and as having a net twist angle, or a netrotation angle, which can refer to, for example, the relative azimuthalangular rotation between an uppermost liquid crystal molecule and alowermost liquid crystal molecule across a specified length, e.g., thelength of a chiral structure or the thickness of the liquid crystallayer. As described herein, a chiral structure refers to a plurality ofliquid crystal molecules in a cholesteric phase that extend in adirection, e.g., a direction perpendicular to the director such as alayer depth direction, and are successively rotated or twisted in arotation direction, e.g., clockwise or counterclockwise. In one aspect,the directors of the liquid crystal molecules in a chiral structure canbe characterized as a helix having a helical pitch.

FIG. 22 illustrates a cross-sectional side view of a cholesteric liquidcrystal (CLC) layer 1004 comprising a plurality of uniform chiralstructures, according to embodiments. In the CLC layer 1004, the chiralstructures that are adjacent in a lateral direction, e.g., x-direction,have similarly arranged liquid crystal molecules. In the illustratedembodiment, the chiral structures 1012-1, 1012-2, . . . 1012-i aresimilarly configured such that liquid crystal molecules of the differentchiral structures that are at about the same depth, e.g., the liquidcrystal molecules closest to the light-incident surface 1004S, have thesame rotation angle, as well as successive rotation angles of successiveliquid crystal molecules at about the same depth, as well as the netrotation angle of the liquid crystal molecules of each chiral structure.

The CLC 1004 comprises a CLC layer 1008 comprising liquid crystalmolecules arranged as a plurality of chiral structures 1012-1, 1012-2, .. . 1012-i, wherein each chiral structure comprises a plurality ofliquid crystal molecules, where i is any suitable integer greater than2. In operation, when incident light having a combination of light beamshaving left-handed circular polarization and light beams havingright-handed circular polarization are incident on the surface 1004S ofthe CLC layer 1008, by Bragg-reflection, light with one of the circularpolarization handedness is reflected by the CLC layer 1004, while lightwith the opposite polarization handedness is transmitted through the CLClayer 1008 without substantial interference. As described herein andthroughout the disclosure, the handedness is defined as viewed in thedirection of propagation. According to embodiments, when the directionof polarization, or handedness of the polarization, of the light beams1016-L, 1016-R is matched such that it and has the same direction ofrotation as the liquid crystal molecules of the chiral structures1012-1, 1012-2, . . . 1012-i, the incident light is reflected. Asillustrated, incident on the surface 1004S are light beams 1016-L havingleft-handed circular polarization and light beams 1016-R having aright-handed circular polarization. In the illustrated embodiment, theliquid crystal molecules of the chiral structures 1012-1, 1012-2, . . .1012-i are rotated in a clockwise direction successively in thedirection in which incident light beams 1016-L, 1016-R travel, i.e.,positive x-direction, which is the same rotation direction as the lightteams 1016-R having right-handed circular polarization. As a result, thelight beams 1016-R having right-handed circular polarization aresubstantially reflected, whereas the light beams 1016-L havingleft-handed circular polarization are substantially transmitted throughthe CLC layer 1004.

As described supra, by matching the handedness of polarization ofincident elliptically or circularly polarized light with the directionof rotation as the liquid crystal molecules of the chiral structures ofa CLC layer, the CLC layer can be configured as a Bragg reflector.Furthermore, one or more CLC layers having different helical pitches canbe configured as a wave-length selective Bragg reflector with highbandwidth. Based on the concepts described herein with respect tovarious embodiments, the CLC layers can be configured as an off-axis oron-axis mirror configured to selectively reflect a first range ofwavelengths, for example, infrared wavelengths (e.g., the nearinfrared), while transmitting another range of wavelengths, e.g.,visible wavelengths.

FIG. 23 illustrates an example of an eye-tracking system 2300 employinga cholesteric liquid crystal reflector (CLCR), e.g., awavelength-selective CLCR 1150 configured to image an eye 302 of aviewer, according to various embodiments. Unlike the CLC layer 1004described above with respect to FIG. 22 , the chiral structures in thewavelength-selective CLCR 1150 that are adjacent in a lateral direction,e.g., x-direction, have differently arranged liquid crystal molecules.That is, the chiral structures are configured such that liquid crystalmolecules of the different chiral structures that are at about the samedepth, e.g., the liquid crystal molecules closest to the light-incidentsurface 1004S, have different rotation angle. As a result, lightincident on the CLCR 1150 is reflected at an angle (O R) relative to thelayer depth direction, as described further below in the context of theeye-tracking system 2300.

Eye tracking can be a useful feature in interactive vision or controlsystems including wearable display systems described elsewhere in thespecification, for virtual/augmented/mixed reality display applications,among other applications. To achieve effective eye tracking, it maydesirable to obtain images of the eye 302 at low perspective angles, forwhich it may in turn be desirable to dispose an eye-tracking camera 702b near a central position of viewer's eyes. However, such position ofthe camera 702 b may interfere with user's view. Alternatively, theeye-tracking camera 702 b may be disposed to a lower position or a side.However, such position of the camera may increase the difficulty ofobtaining robust and accurate eye tracking since the eye images arecaptured at a steeper angle. By configuring the CLCR 1150 to selectivelyreflect infrared (IR) light 2308 (e.g., having a wavelength of 850 nm)from the eye 302 while transmitting visible light 2304 from the world,the camera 702 b can be placed away from the user's view while capturingeye images at normal or low perspective angles. Such configuration doesnot interfere with user's view since visible light is not reflected. Thesame CLCR 1150 can also be configured as an IR illumination source 2320by reflecting IR light from an IR source, e.g., IR LED, into the eye302, as illustrated. A low perspective angle of IR illuminator canresults in less occlusions, e.g., from eye lashes, which configurationallows more robust detection of specular reflections, which can beuseful feature in modern eye-tracking systems.

Still referring to FIG. 23 , according to various embodiments, the CLCR1150 comprises one or more cholesteric liquid crystal (CLC) layers eachcomprising a plurality of chiral structures, wherein each chiralstructure comprises a plurality of liquid crystal molecules that extendin a layer depth direction (e.g., z-direction) and are successivelyrotated in a first rotation direction, as described supra. Thearrangements of the liquid crystal molecules of the chiral structuresvary periodically in a lateral direction perpendicular to the layerdepth direction such that the one or more CLC layers are configured tosubstantially Bragg-reflect a first incident light having a firstwavelength (λ₁) while substantially transmitting a second incident lighthaving a second wavelength (λ₂). As described above, each of the one ormore CLC layers are configured to substantially Bragg-reflectelliptically or circularly polarized first and second incident lighthaving a handedness of polarization that is matched to the firstrotation direction, when viewed in the layer depth direction, whilebeing configured to substantially transmit elliptically or circularlypolarized first and second incident light having a handedness ofpolarization that is opposite to the first rotation direction, whenviewed in the layer depth direction. According embodiments, thearrangements of the liquid crystal molecules varying periodically in thelateral direction are arranged to have a period in the lateral directionsuch that a ratio between the first wavelength and the period is betweenabout 0.5 and about 2.0. According to embodiments, the first wavelengthis in the near infrared range between about 600 nm and about 1.4 μm, forinstance about 850 nm and the second wavelength in is in the visiblerange having one or more colors as described elsewhere in thespecification. According to various embodiments, the liquid crystalmolecules of the chiral structures are pre-tilted relative to adirection normal to the layer depth direction. As configured, the one ormore CLC layers are configured such that the first incident light isreflected at an angle (O R) relative to the layer depth direction(z-direction) exceeding about 50°, about 60°, about 70° or about 80°degrees relative to the layer depth direction.

Thus configured, the wavelength-selective CLCR 1150 comprises one ormore cholesteric liquid crystal (CLC) layers each comprising a pluralityof liquid crystal molecules that extend in a layer depth direction andare successively rotated in a first rotation direction, whereinarrangements of the liquid crystal molecules of the chiral structuresvary periodically in a lateral direction perpendicular to the layerdepth direction such that the one or more CLC layers are configured tosubstantially Bragg-reflect a first incident light having a firstwavelength, e.g., an IR wavelength, while substantially transmitting asecond incident light having a second wavelength, e.g., a visiblewavelength.

Similar liquid crystal layers and structures may be used for thereflector 996 and coating 998 described above in connection with FIGS.17-20E. The coating 998 may for example comprise a liquid crystalcoating and may be wavelength and/or polarization selective in certainimplementations. Other types of coatings 998 and reflectors 996,however, may be employed.

As discussed above, for example, in connection with FIG. 16 , a lens 980may be used to alter the propagation of (e.g., collimate) light directedto the coupling optical element 944. This light may be light reflectedfrom, for example, the user's eye such as an anterior surface (e.g.,corneal surface) of the user's eye. The distance from the eye, e.g., theanterior surface (e.g., corneal surface) to the coupling optical element944 may be for example about 20 mm. A positive lens 980 such as a lenshaving a focal length of about 20 mm may be configured to collimatelight reflected from the eye 210, such as an anterior portion of the eye(e.g., the cornea). Light reflected form the anterior surface eye may becoupled into the waveguide 940 and guided therein to a camera. With thefocal length set at the distance to the anterior surface of the eye, thecamera can image such surfaces. Accordingly, in various implementationsthe positive lens 980 therefore may have a focal length that is equal orsubstantially equal to the distance of the lens to the portion of theeye 210 to be imaged, e.g., the cornea.

Although a refractive optical element is shown, other types of lenses oroptical elements with optical power such as positive optical power maybe used. For example, the lens may comprises a diffractive opticalelement such as a diffractive lens or hologram. Such a lens may bedisposed between the eye and the coupling optical element 944 in someimplementations.

In various implementations, the coupling optical element 944 may includeoptical power. The coupling optical element 944 may, for example,comprise a diffractive optical element having optical power. Thediffractive optical element may comprises, for example, a diffractivegrating. The diffractive optical element may comprise a holographicoptical element or a hologram. The diffractive optical element may havediffractive features such as for example surface features that areconfigured to both turn light into the waveguide and to provide opticalpower. Other types of diffractive optical elements are possible. Invarious implementations, the diffractive optical elements may compriseliquid crystal and may comprises liquid crystal gratings. Thediffractive optical elements may also comprise polarization grating.Additionally, the diffractive optical elements may comprise liquidcrystal polarization gratings. Some nonlimiting examples of liquidcrystal gratings, liquid crystal polarization gratings and other liquidcrystal optical elements are discussed in the following publishedapplications, each of which is hereby incorporated by reference hereinin its entirety and for all purposes: U.S. Publication No. 2018/0143438,titled “MULTILAYER LIQUID CRYSTAL DIFFRACTIVE GRATINGS FOR REDIRECTINGLIGHT OF WIDE INCIDENT ANGLE RANGES,” filed on Nov. 16, 2017; U.S.Publication No. 2018/0143485, titled “SPATIALLY VARIABLE LIQUID CRYSTALDIFFRACTION GRATINGS,” filed on Nov. 16, 2017; U.S. Publication No.2018/0143509, titled “WAVEGUIDE LIGHT MULTIPLEXER USING CROSSEDGRATINGS,” filed on Nov. 16, 2017; U.S. Publication No. 2018/0239177,titled “VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIONCONVERSION,” filed on Feb. 22, 2018; and U.S. Publication No.2018/0164627, titled “DIFFRACTIVE DEVICES BASED ON CHOLESTERIC LIQUIDCRYSTAL,” filed on Dec. 7, 2017.

This diffractive optical element may have optical power that alters onthe propagation of light incident thereon. The diffractive opticalelement, may for example, collimate light reflected from as surfacehaving a distance from said diffractive optical element corresponding tothe focal length of the diffractive optical element. Such distance maybe for example from about 15 to 20 mm (e.g., 20 mm or thereabouts). Sucha focal length may provide for collimating light reflected from ananterior surface of the eye such as a corneal surface (e.g., cornea).Other distances are possible. For example the distance may be in a rangefrom about 10 to 40 mm or 10 to 50 mm, 5 to 40 mm or 5 to 50 mm or anyrange between any of the distance values herein. Values outside theseranges are also possible.

FIG. 24 shows an example, of a coupling optical element (e.g., couplinggrating) 2111 disposed on a waveguide 2102 of an eyepiece 950. Thecoupling optical element 2111 comprises a diffractive optical elementconfigured to couple light incident thereon into the waveguide 2102. Thediffractive optical element also includes optical power. For example,the diffractive optical element includes diffractive features such assurface diffractive features that are configured to provide opticalpower, for example, to collimate light incident thereon from an anteriorsurface of the eye (e.g., corneal surface). A light consolidatingelement 2116, and an outcoupling optical element 2120 are also showndisposed on the waveguide 2102. The light consolidating element 2116 isdisposed to receive light coupled into the waveguide 2102 by thecoupling element 2111. The light consolidating element 2116 isconfigured to redirect light incident thereon from the coupling opticalelement 2111 to the out-coupling optical element 2120. The lightconsolidating element 2116 is configured to reduce lateral spatialextent of light (e.g., the light beam) from said at least one couplingelement prior to reaching said at least one out-coupling opticalelement, and an outcoupling optical element 2120. In certainconfigurations, fewer optical elements may be used, possibly, forexample, to reduce cost and/or optical losses or for other reasons. Forexample, the light consolidating element 2116 may be omitted in certainembodiments. In such embodiments, light may be incoupled from the inputcoupling element 2111 (e.g., after being reflected from the eye 210) anddirectly coupled to the outcoupling optical element 2120. The light maypropagate through the eyepiece 950 between the input coupling element2111 and the outcoupling optical element 2120. Other configurations arepossible. A camera is disposed with respect to the out-coupling opticalelement 2120 to receive light therefrom. The out-coupling opticalelement 2120 is configured to direct light received from the lightconsolidating element 2116 to the camera for capturing an image.

FIG. 24 also shows incoupling optical element 2104, a light distributingelement 2108, and an image content out-coupling optical element 2110disposed on the waveguide 2102. The incoupling optical element 2104 maybe configured to couple light received from an image projector into thewaveguide 2102. The light distribution element 2108 may be configured toredirect light received from the incoupling optical element 2104 to theout-coupling optical element 2110, additionally increasing the spatialextent of the light as discussed above. The out-coupling optical element2110 may be configured to couple light guided within the waveguide 2102out of the waveguide and direct such light to the eye for viewing imagecontent from the projector.

In various implementations one or more of these optical elements 2111,2116, 2120, 2110, 2108, 2104 may be disposed within or on a waveguide2102. Similarly, as discussed above, one or more of these opticalelements 2111, 2116, 2120, 2110, 2108, 2104 may comprise diffractiveoptical elements.

In the implementation illustrated in FIG. 24 , the coupling opticalelement (e.g., coupling grating) 2111 may be displaced lateral from theout-coupling optical element 2110 on the waveguide 2102. In theimplementation shown, a space laterally separates the coupling opticalelement 2111 from the out-coupling optical element 2110.

FIG. 25 shows another similar implementations wherein the couplingoptical element (e.g., coupling grating) 2111 is displaced laterallyfrom the out-coupling optical element 2110 on the waveguide 2102. In theimplementation shown in FIG. 25 , however, a space does not laterallyseparate the coupling optical element 2111 from the out-coupling opticalelement 2110.

Having the coupling optical element (e.g., coupling grating) 2111displaced laterally from the out-coupling optical element 2110 on thewaveguide 2102 can enable the coupling optical element to includeoptical power, for example, that collimates light received from ananterior surface of the eye (e.g., corneal surface) such that thisoptical power does not affect the propagation of light from and/orthrough the out-coupling optical element 2110 to the eye. Imagespresented to the eye from the image projector as well as the view of theenvironment in front of the user and the head mounted display, need nottherefore be affected (e.g., distorted or defocused, etc.) by theoptical power of the coupling optical element 2111.

FIG. 26 illustrates an implementation of an imaging system 900configured to image multiple portions of the eye. For example, animaging system 900 such as shown in FIG. 26 may be configured to imageboth anterior surfaces of the eye (e.g., corneal surfaces) as well asthe retina. The imaging system 900 includes a pair of incoupling opticalelements, a first incoupling optical element 2111 a and a secondincoupling optical element, disposed on the waveguide 2102 of theeyepiece. The imaging system 900 additionally includes a pair of lightconsolidating elements, a first light consolidating optical element 2116a and a second light consolidating element 2116 b, disposed on thewaveguide 2102. In certain configurations, fewer optical elements may beused, possibly, for example, to reduce cost and/or optical losses or forother reasons. For example, the light consolidating elements 2116 a,2116 b may be omitted in certain embodiments. In such embodiments, lightmay be incoupled from the first and second input coupling elements 2111a, 2111 b (e.g., after being reflected from portions the eye 210 such asthe retina and/or cornea) and directly coupled to corresponding firstand second outcoupling optical elements 2120 a, 2120 b. The light maypropagate through the eyepiece 950 (e.g., via a waveguide such as thewaveguide 2102) between the first and second input coupling elements2111 a, 2111 b and the corresponding outcoupling optical elements 2120a, 2120 b. Other configurations are possible. In addition, the imagingsystem 900 additionally includes a pair of light out-coupling opticalelements, a first out-coupling optical element 2120 a and a secondout-coupling optical element 2120 b, disposed on the waveguide 2102.

The first coupling optical element 2111 a is configured to couple lightincident thereon into the waveguide 2102. The first light consolidatingelement 2116 a is disposed to receive light coupled into the waveguide2102 by the first coupling element 2111 a. The first light consolidatingelement 2116 a is configured to redirect light incident thereon from thefirst coupling optical element 2111 a to the first out-coupling opticalelement 2120 a. The first light consolidating element 2116 a is alsoconfigured to reduce the lateral spatial extent of light (e.g., thelight beam) from the first coupling element 2111 a prior to reaching thefirst out-coupling optical element 2120 a. A camera is disposed withrespect to the first out-coupling optical element 2120 a to receivelight therefrom. Although the camera is not shown in FIG. 26, an areacorresponding to the detection area 2130 of the camera is shown. Thefirst out-coupling optical element 2120 a is configured to direct lightreceived from the first light consolidating element 2116 a to the cameraand, in particular, to the detection area 2130 shown in FIG. 26 , forcapturing an image.

Likewise, the second coupling optical element 2111 b is configured tocouple light incident thereon into the waveguide 2102. The second lightconsolidating element 2116 b is disposed to receive light coupled intothe waveguide 2102 by the second coupling element 2111 b. The secondlight consolidating element 2116 b is configured to redirect lightincident thereon from the second coupling optical element 2111 b to thesecond out-coupling optical element 2120 b. The second lightconsolidating element 2116 b is also configured to reduce the lateralspatial extent of light (e.g., the light beam) from the second couplingelement 2111 a prior to reaching the second out-coupling optical element2120 a. A camera is disposed with respect to the second out-couplingoptical element 2120 b to receive light therefrom. Although the camerais not shown in FIG. 26 , an area corresponding to the detection area2130 of the camera is shown. The second out-coupling optical element2120 b is configured to direct light received from the second lightconsolidating element 2116 b to the camera and, in particular, to thedetection area 2130 shown in FIG. 26 for capturing an image.

FIG. 26 also shows incoupling optical element 2104, a light distributingelement 2108, and an image content out-coupling optical element 2110disposed on the waveguide 2102. The incoupling optical element 2104 maybe configured to couple light received from an image projector into thewaveguide 2102. The light distribution element 2108 may be configured toredirect light received from the incoupling optical element 2104 to theout-coupling optical element 2110, additionally increasing the spatialextent of the light as discussed above. The out-coupling optical element2110 may be configured to couple light guided within the waveguide 2102out of the waveguide and direct such light to the eye for viewing imagecontent from the projector.

In the implementation illustrated in FIG. 26 , the first and secondcoupling optical elements (e.g., coupling gratings) 2111 a, 2111 b aredisplaced lateral from the out-coupling optical element 2110 on thewaveguide 2102. In the implementation shown, a space laterally separatesthe first and second coupling optical elements 2111 a, 2111 b from theout-coupling optical element 2110. Furthermore, in the example of FIG.26 , the first and second coupling optical elements 2111 a, 2111 b aredisplaced lateral from each other on the waveguide 2102. In otherimplementations, two or more of the first coupling optical element(e.g., coupling grating) 2111 a, the second coupling optical element2111 b, and the out-coupling optical element 2110 need not be displacedlaterally from each other on the waveguide 2102.

In various implementations one or more of these optical elements 2111 a,2111 b, 2116 a, 2116 b, 2120 a, 2120 b, 2110, 2108, 2104 may be disposedwithin or on a waveguide 2102. Similarly, as discussed above, one ormore of these optical elements 2111 a, 2111 b, 2116 a, 2116 b, 2120 a,2120 b, 2110, 2108, 2104 may comprise diffractive optical elements.

The imaging system 900 of FIG. 26 can be configured to image multipleportions of the eye. For example, an imaging system 900 may beconfigured to image both anterior surfaces of the eye (e.g., cornealsurfaces) as well as the retina. The first incoupling optical element2111 a may, for example, have optical power or have a lens disposed infront thereof with optical power. The first coupling optical element2111 a may, for example, comprise a diffractive optical elementconfigured to couple light into the waveguide 2102 but also configuredto impart optical power thereto. Additionally or alternatively, a lenshaving optical power may be disposed in front of the first couplingoptical element 2111 a. The optical power may be configured to alter thepropagation of light received by the first incoupling optical element2111 a such that a particular portion of the eye may be imaged. In someexamples, the optical power may be positive optical power. Moreover, theoptical power may be such that an anterior surface of the eye may beimaged. The optical power may, for example, correspond to a focal lengthof between about 15 to 25 mm (e.g., about 20 mm). As a result, lightreflected from an anterior surface of the eye, which may be about 15 to25 mm (e.g., about 20 mm) from the first coupling optical element 2111 amay be collimated and coupled into the waveguide. Other focal lengthsare possible. For example the focal length may be in a range from about10 to 40 mm or 10 to 50 mm, 5 to 40 mm or 5 to 50 mm or any rangebetween any of the distance values herein. Values outside these rangesare also possible.

In contrast, in various implementations, the second coupling opticalelement 2111 b may neither have optical power nor include a lensdisposed in front thereof. The lack of optical power associated with thesecond coupling optical element 2111 b will result in light from theanterior portion of the eye (e.g., corneal surfaces) not beingcollimated and not being imaged by the camera. However, light reflectedfrom the retina may upon passing through the natural lens of the eye ofthe user may be collimated. This light collimated by the natural lens ofthe eye may be coupled into the waveguide 2102 by the second couplingoptical element 2111 b and imaged by the camera. In this manner, lightcollected by the first coupling optical element 2111 a may image ananterior surface of the eye (e.g., a corneal surface of the eye) and thesecond coupling optical element 2111 b may image the retina of the eyeof the user. In some implementations, such a configuration enables lightcollected by the first coupling optical element 2111 a to form images ofglint on the eye, for example, on an anterior surface of the eye (e.g.,a corneal surface of the eye). The second coupling optical element 2111b may image the retina of the eye of the user as discussed above. Insome examples, the second coupling optical element 2111 b and/or a lensdisposed in front thereof may have some amount of net optical power(e.g., a non-zero amount of net optical power) that is weaker than thatof the first coupling optical element 2111 a and/or a lens disposed infront of the first coupling optical element 2111 a. In particular, thesecond coupling optical element 2112 b can have optical power and/or alens associated therewith, however, total optical power of the secondcoupling optical element 2112 b and/or any lens associated secondcoupling optical element is less than the optical power of the firstcoupling optical element and/or any lens associated with the firstcoupling optical element).

In some implementations, the images formed by light collected by thefirst coupling optical element 2111 a are next to (e.g., notsuperimposed over) images formed by light collected by the secondcoupling optical element 2111 b. For example, images of the anteriorsurface(s) of the user's eye (e.g., cornea) may be formed next to (e.g.,not superimposed over) images of the retina.

Polarization techniques can be used to attenuate or remove light fromthe anterior surfaces (e.g., corneal surfaces) from affecting imagesformed by light collected by the second coupling optical element 2111 b.For example, the eye can be illuminated with polarized light having afirst polarization and the camera can form an image using light from thesecond out-coupling optical element 2120 b using light of a seconddifferent polarization. For example, the second out-coupling opticalelement 2111 b may be a polarization selective coupling element thatselectively couples out light of the second polarization different thanthe first polarization. Additionally or alternatively, a polarizer 2140that filters out the first polarization (e.g., selectively transmits thesecond polarization) may be included between the second out-couplingoptical element 2120 b and the camera 920 as illustrated in FIG. 27 ,which is a cross-section through the waveguide 950, 2102, consolidatingoptical elements 2116 a, 2116 b, and out-coupling optical elements 2120a, 2120 b shown in FIG. 26 .

Such a configuration may be used to reduce unwanted reflections (e.g.,glint), such as from the cornea when imaging the retina. Reflection fromthe cornea will be specular. Accordingly, if light of the firstpolarization is incident on the cornea, the light reflected from thecornea will retain that first polarization. In contrast, the retina isdiffuse. If light of the first polarization is incident on the retina,the light reflected from the retina does not retain solely the firstpolarization. The diffuse reflection more likely results in unpolarizedlight. Accordingly, the second polarization, different from the firstpolarization will be present in the light reflected from the retina. Asa result, by forming images with light coupled out of the secondout-coupling optical element 2120 b using light of the secondpolarization, images of the retina will be obtained while images of thecornea or glint will be suppressed. Likewise, by illuminating with afirst polarization and imaging with a second different polarization, theretina can be image with reduced glare from the cornea.

Accordingly, in various implementations, polarization specific opticalfilters or polarization selective optical elements (e.g. couplinggratings) may be used to reduce unwanted reflected light from the eye210 (e.g., from the cornea). For example, unwanted light, glare, orglint may be reflected off the cornea that may saturate an imagecaptured by the camera. As discussed above, light reflected from thecornea may be specular and maintain its polarization. By contrast, lightreflected off the retina may be more diffusely reflected and may be lesshomogenously polarized. Likewise, a combination of polarizers may beused to remove some or most of the unwanted light reflected from thecornea. Initially polarized light can be used for illuminating the eyeof the user. In some designs, a polarized illumination source (e.g., thelight source) may be used. Additionally or alternatively, a firstpolarizer (e.g., a polarization specific optical filter or apolarization selective optical coupling element coupling illuminationlight into an illumination waveguide) may be positioned at the beginningof the optical path of the illumination source to provide initialpolarization of the light to the eye. A second polarizer (e.g., apolarization specific optical filter or polarization selective couplingelement) may be positioned at the optical path before the light entersthe camera. The second polarizer may be rotated at 90° from the firstpolarizer (e.g. the polarizers may be “crossed”). As a result, the eyewill be illuminated with the first polarization with some light of thefirst polarization reflected from the cornea. This light will not passthrough the crossed polarizer (that preferentially passes light of thesecond polarization) located proximal the camera. However, lightreflected from the retina will include the second polarization.Likewise, light diffusely reflected from the retina will pass throughthe polarizer 2140 proximal the camera and will enable an image of theretina to be captured by the camera. Thus, in such configurations,unwanted light received from the eye (e.g., from cornea) and enteringthe camera may be reduced or eliminated from the images captured usinglight from the second coupling optical element 2111 b. Otherconfigurations are possible. For example, a polarization selectivecoupling elements 2111 b and/or a polarization selective out-couplingoptical elements 2120 b may be used in addition or in alternative topolarizers such as the polarizer 2140 proximal the camera. Additionallyor alternatively, a polarized light source may be used for illumination(e.g., illuminating the eye). The effect may again be to reduce orremove unwanted light received from the eye (e.g., from cornea) beforeentering the imaging device 920.

As illustrated in FIG. 27 , in various implementations, such polarizersare not used in an optical path from the first coupling optical element2111 a and the camera or between the first out-coupling optical element2120 a and the camera. As a result, images of the cornea and glint maybe obtained from light coupled by the first coupling optical element2111 a into the waveguide and/or light coupled out of the waveguide fromthe first out-coupling optical element 2120 a. As discussed above, thisfirst coupling optical element 2111 a may have optical power or a lensassociated therewith that is specifically used to image the corneaand/or glint. Likewise, polarization selective coupling optical elements2111 a or polarization selective out-coupling optical element 2120 athat filter out light of the first polarization would not be used as thefirst coupling optical element 2111 a and out-coupling optical element2120 a, respectively. Additionally, polarizers 2140 between the couplingoptical element 2111 a and the camera 920 or between the out-couplingoptical element 2111 a and the camera 920 that filter out light of thefirst polarization would not be used.

A wide variety of variations are possible. For example, although thefirst and second out-coupling optical elements 2120 a, 2120 b aredescribed above as coupling light and forming images on a single camera(e.g., a single detection area 2130), in other implementations, thefirst and second out-coupling optical elements 2120 a, 2120 b cancoupling light and forming images on respective first and secondcameras. Other variations are possible.

Additionally, in some implementations, one or more of the eyepiecesdescribed above (e.g., the eyepiece 950) with reference to FIGS. 24-27may be a dedicated imaging eyepiece layer (e.g., omitting the incouplingoptical element 2104, the light distributing element 2108, and/or theoutput coupling element 2110). In such implementations, the imagingeyepiece layer may be included as a layer in a stack of waveguides. Theone or more other layers in the stack of waveguides may include theincoupling optical element 2104, the light distributing element 2108,and/or the output coupling element 2110.

In some embodiments, the dedicated imaging eyepiece layer can beconfigured to capture images of the environment. In some suchembodiments, the imaging eyepiece layer may be disposed most proximal tothe environment when installed in the head-mounted display. In some suchconfigurations, the dedicated imaging eyepiece layer may be theoutermost layer in the waveguide stack such that it is positionedbetween the other layers (e.g., waveguides) and the environment. In someembodiments, the dedicated imaging eyepiece layer can be configured tocapture images of the user's eye 210. In some such embodiments, theimaging eyepiece layer may be disposed most proximal to the user wheninstalled in the head-mounted display. In some implementations, thededicated imaging eyepiece layer may be the innermost layer in thewaveguide stack such that it is positioned between the other layers(e.g., waveguides) and the user. Other configurations are possible.

In certain embodiments, the first and second coupling elements 2111 a,2111 b may be laterally aligned but displaced in depth (e.g., along thez-axis or into the page of FIG. 26 ). For example, in such embodiments,the first and second coupling elements 2111 a, 2111 b may be positionedon opposite sides of the same waveguide. In certain embodiments, thefirst input coupling element 2111 a may be disposed on or within a firstwaveguide and the second input coupling element 2111 b may be disposedon or within a second waveguide. Additionally or alternatively, thefirst and second light consolidating elements 2116 a, 2116 b and/or thefirst and second outcoupling optical elements s 2120 a, 2120 b may bedisposed on opposite sides of the same waveguide and/or may be disposedon or in corresponding separate waveguides.

One or more of the coupling optical elements 2111, 2111 a, 2111 bdescribed above with reference to FIGS. 24-27 may bewavelength-selective such that the optical elements are configured tointeract only with a certain wavelength or band of wavelengths. Thewavelength or band of wavelengths may include invisible light (e.g.,infrared light, or a specific band thereof). In some implementations,the first input coupling element 2111 a may be configured to operate ona wavelength lower than that for the second input coupling element 2111b (or vice versa). For example, the first coupling optical element 2111a may be configured to interact with about 800 nm light, and/or thesecond coupling optical element 2111 b may be configured to interactwith about 950 nm light (or vice versa). Optical filters may also be useto effectuate similar wavelength selectivity. In variousimplementations, therefore, light coupled into the waveguide by thefirst coupling optical element that reaches the at least one camera canbe of a different wavelength than light coupled into the waveguide bythe second optical element that reaches the at least one camera. Otherconfigurations are possible.

A wide variety of variations are possible in the structure and design ofthe coupling optical elements 2120 and the out-coupling optical elements2012. For example, the size and shape of the coupling optical element2120 for coupling light into the waveguide 2102 and the out-couplingoptical element 2112 for coupling light out of the waveguide 2102 to acamera, and in particular the size and shape of the coupling areas ofthe coupling optical element 2120 and out-coupling optical element 2112,can be varied. Coupling area as used herein refers to the area of theoptical element that is configured to receive light and couple saidlight into the waveguide or out of the waveguide for use by the systemfor example for imaging (e.g., the eye or the environment in front ofthe user). In some implementations, the coupling area may corresponds tothe area of the optical element in its entirety or to a portion of thearea of the optical element that is configured to be used in the systemto couple light into or out of the waveguide for use by the system. Forexample, in some implementations, the coupling area of a couplingelement comprising a diffractive optical element used to couple light(from the eye or the environment in front of the user) into thewaveguide is that area of the diffractive optical element used by thesystem to couple light into the waveguide. The coupling optical element,for example, the diffractive grating or diffractive optical element maybe larger than the coupling area in some cases. For example, opaqueobjects such as an opaque element or layer having a small aperturetherein may obstruct the propagation of light to portions of thediffractive grating or diffractive optical element thereby reducing thecoupling area. Accordingly, the size and shape of the coupling area maybe controlled by the size and perimeter of the optical element (e.g.,the spatial extent of the diffractive optical element or grating) aswell as other optical elements or other components or features that mayblock light from reaching portions of the optical element. Other factorsmay potentially reduce, alter or otherwise influence the size and shapeof the coupling area.

FIGS. 28A and 28B show a coupling optical element 2120 for couplinglight into the waveguide 2102 wherein the coupling optical element has areduced size. In particular, the coupling optical element 2120 has apinhole size coupling area. The size of the coupling area may forexample be about 1.5 mm×1.5 mm. As illustrated in FIG. 28A, for example,coupling area of the coupling optical element 2120 may have a length, L,and thickness, T. The length and thickness may both be about 1.5 mm incertain implementations. The reduced size of the coupling area removesmultiple (e.g. ghost) images from being collected by the couplingoptical element 2120. The pinhole size coupling area of the couplingoptical element 2120 for coupling light from an object such as theuser's eye or an object in the environment in front of the user and theeyewear has an effect similar to that of a pinhole camera on thecollection of light and resultant imaging. The reduced coupling areasize of the coupling optical element 2120 is akin to the reduced size ofa pinhole camera coupling area. The result is that a large depth offocus or depth of field is provided without the need for a lens. Thecoupling optical element 2120 also need not have optical power nor doesa lens need to be provided at the coupling optical element 2120.Nevertheless a large range of object distances are in focus with such adesign.

The out-coupling optical element 2112 shown in FIGS. 28A and 28B forcoupling light out of the waveguide 2102 to a camera is also of reducedsize. In this particular implementation, the size and shape of thecoupling optical element 2120 and the out-coupling optical element 2112are similar or the same. The out-coupling optical element 2112 may alsobe 1.5×1.5 mm.

As discussed above, the coupling optical element 2120 and theout-coupling optical element 2112 may comprise diffractive opticalelements such as diffraction gratings. The coupling optical element 2120and the out-coupling optical element 2112 may comprise holograms orholographic optical elements. As discussed herein, the coupling opticalelement 2120 and the out-coupling optical element 2112 may compriseliquid crystal, liquid crystal gratings, polarization gratings and/orliquid crystal polarization gratings. The coupling optical element 2120may be configured to receive light (e.g., from the eye of the user orfrom the environment in front of the user) and couple at least a portionof that light into the waveguide 2102. The coupling optical element 2120may also be configured to turn and direct a portion of the light to theout-coupling optical element 2112. The out-coupling optical element 2112may be configured to couple light received from the coupling opticalelement 2120 and guided within the waveguide 2102 out of the waveguide,for example, to a camera. In the configuration shown, a lightconsolidating optical element such as described above is not included.

The size and shape of the coupling area of the coupling optical element2120 and the out-coupling optical element 2112 may vary. For example,although the coupling optical element 2120 and the out-coupling opticalelement 2112 are shown as squares, the shapes of either or both may bedifferent. In some implementations, the size and relative placement ofeach of optical elements 2120, 2112 may be selected based at least inpart on the desired distance from the user's eye (i.e., focal length),the wavelength of the light to be captured, or both. The desireddistance between the waveguide and the user's eye may be, for example,from about 15 mm to 25 mm. Other configurations are possible. In someembodiments, the optical elements 2120, 2112 may, for example, bedisposed 15 mm to 25 mm away from each other on or in the waveguide. Theshape of the coupling area may, for example, be circular or otherwiseround. The size of the coupling area may also be different. For example,the dimension (e.g., average or maximum) along one direction of thecoupling area (e.g., length, L, or thickness, T) may be from 0.1 to 3mm, 0.1 to 0.3 mm, 0.1 to 0.5 mm, 0.5 to 3 mm, 0.5 to 2 mm, from 1 to 3mm, from 1 to 2 mm, from 0.5 to 2.5 mm, from 1.0 to 2.5 mm, from 1.0 mmto 1.5 mm or 1.5 mm to 2 mm or any range formed by any of these values.Values outside these ranges are also possible. Similarly, dimensions(e.g., maximum or average) along another direction of the coupling area(e.g., length, L, or thickness, T) may be from 0.1 to 3 mm, 0.1 to 0.3mm, 0.1. to 0.5 mm, 0.5 to 3 mm, 0.5 to 2 mm, from 1 to 3 mm, from 1 to2 mm, from 0.5 to 2.5 mm, from 1.0 to 2.5 mm, from 1.0 mm to 1.5 mm or1.5 mm to 2 mm or any range formed by any of these values. Valuesoutside these ranges are also possible. These two directions may beorthogonal in some implementations. The dimensions along the twodirections need not be the same. Accordingly, the coupling area may besymmetrical or asymmetrical. For example, the aspect ratio of thecoupling area (e.g., as measured by the ratio of the length to thicknesssuch as maximum length to maximum thickness or average length to averagethickness) may be from 1 to 2, from 1 to 1.75, from 1 to 1.5, from 1 to1.3, from 1 to 1.2, from 1 to 1.1 or any range formed by any of thesevalues. Values outside these ranges are also possible.

As discussed above, other shapes are possible. FIGS. 29A and 29B, forexample, show a coupling optical element 2120 for coupling light intothe waveguide 2102 and an out-coupling optical element 2112 for couplinglight out of the waveguide to a camera wherein the coupling opticalelement 2120 has an arcuate slit-shaped coupling area. (The outcouplingoptical element 2112 has a pinhole coupling area similar to that shownin FIGS. 28A and 28B.)

A slit may be advantageous in being larger than a pinhole and thereforemay collect more light. However, the narrowness of the slit provides asimilar effect as a pinhole. For example, the reduced thickness, T, ofthe coupling area may remove multiple images from being collected by thecoupling optical element 2120. Ghost images and/or blur can thereby bereduced. As illustrated in FIG. 25A, the coupling area of the couplingoptical element 2120 may have a length, L, and thickness, T. Thethickness, T, may be about 1.0 mm or 1.5 mm in certain implementations.The pinhole size thickness, T, of the coupling optical element 2120 forcoupling light from an object such as the eye or an object in theenvironment in front of the user and the eyewear has an effect similarto that of a pinhole camera on the collection of light and resultantimaging. The reduced size of the coupling area of the coupling opticalelement 2120 is akin to the reduce size of a pinhole camera couplingarea. The result is that a large depth of focus or depth of field isprovided without the need for a lens. The coupling optical element 2120also need not have optical power nor does a lens need to be provided atthe coupling optical element 2120. Nevertheless, a large range of objectdistances are in focus with such a design.

The out-coupling optical element 2112 shown in FIGS. 29A and 29B forcoupling light out of the waveguide to a camera is also of reduced size.In this particular implementation, the size and shape of theout-coupling optical element 2112 are similar or the same as thatdescribed above in connection with FIGS. 28A and 28B. The out-couplingoptical element 2112, for example, may also be 1.5×1.5 mm.

As discussed above, the coupling optical element 2120 and theout-coupling optical element 2112 may comprise diffractive opticalelements such as diffraction gratings. The coupling optical element 2120and the out-coupling optical element 2112 may comprise holograms orholographic optical elements. As discussed herein, the coupling opticalelement 2120 and the out-coupling optical element 2112 may compriseliquid crystal, liquid crystal gratings, polarization gratings, liquidcrystal polarization gratings or any combination thereof. The couplingoptical element 2120 may be configured to receive light (e.g., from theeye of the user or from the environment in front of the user) and coupleat least a portion of that light into the waveguide 2102. The couplingoptical element 2120 may also be configured to turn and direct a portionof the light to the out-coupling optical element 2112. The out-couplingoptical element 2112 may be configured to couple light received from thecoupling optical element 2120 and guided within the waveguide 2102 tothe out-coupling optical element 2112 out of the waveguide, for example,to a camera. In the configuration shown, a light consolidating opticalelement such as described above is not included.

The shape of the coupling area of the coupling optical element 2120 andthe out-coupling optical element 2112 may vary. In theory, a curved slitmay potentially facilitate directing the light from the coupling opticalelement 2120 to the out-coupling optical element. Moreover, in someimplementations, the arcuate slit may have a curvature described by aradius of curvature and a center of curvature. The curvature of the slitmay be such that the out-coupling optical element 2112 is at the centerof curvature of the arcuate-shape slit. However, the curvature may bedifferent, for example, larger or smaller. Still other variations in theshape are possible. For example, the edges of the arcuate shaped slitmay be rounded.

The size of the coupling area may also be different. For example, theshorter dimension, the thickness, T, along one direction of the couplingarea may be from 0.1 to 0.3 mm, 0.1 to 0.5 mm, 0.3 to 0.5 mm, 0.2 to 0.5mm, 0.1 to 1.0 mm, 0.3. to 1.0, 0.5 to 3 mm, 0.5 to 2 mm, from 1 to 3mm, from 1 to 2 mm, from 0.5 to 2.5 mm, from 1.0 to 2.5 mm, from 1.0 mmto 1.5 mm or 1.5 mm to 2 mm or any range formed by any of these values.Values outside these ranges are also possible. This dimension, thethickness, T, may be smaller than the other dimension, the length, L.The other dimension, length, L, may correspond to the length orresultant displacement from one end to another. Alternately, a pathlength, P, or in this case an arc length, may be used to provide ameasure of the larger dimension of the coupling area. In someimplementations, the length, L, or path length or arc length, P, may befrom 5 mm to 40 mm, 10 to 40 mm, from 10 to 30 mm, from 15 to 30 mm,from 15 to 25 mm, from 1 to 5 mm, from 3 to 5 mm, or any range formed byany of these values. Values outside these ranges are also possible.These two directions may be orthogonal in some implementations, however,the directions need not be orthogonal. The slit is asymmetric. Forexample, the aspect ratio of the coupling area (e.g., as measured by theratio of the length, L, to thickness where length can be either theresultant displacement from one end to another or the path length suchas the arc length, P) may be from 5 to 100, from 10 to 100, from 15 to100, from 20 to 100, from 10 to 40, from 10 to 50 or any range formed byany of these values. Values outside these ranges are also possible. Insome embodiments, the dimension along one direction of the coupling areaof the coupling optical element 2120 may be less than or equal to 2.5%of the distance between the center of the coupling optical element 2120and the center of the out-coupling optical element 2112. By way ofexample, the center-to-center distance between optical elements 2120,2112 may be about 20 mm and said dimension (e.g., thickness, T) may beless than or equal to about 0.5 mm (e.g., 2.5% of 20 mm). Otherconfigurations or values are possible. For example, said dimension(e.g., thickness, T) may be less than or equal to 2%, 1.5%, and/or 1% ofthe distance between the center of the coupling optical element 2120 andthe center of the out-coupling optical element 2112. The dimensionsreferred to herein such as thickness, T, length, L, path length P, maybe single measurements, averages, maximums or minimums.

The shape and size of the out-coupling optical element 2112 may also bevary. For example, although the out-coupling optical element 2112 areshown as squares, the shapes may be different. The shape of the couplingarea may, for example, be circular or otherwise round. The size of thecoupling area may also be different. For example, the dimension, e.g.thickness, T, along one direction of the coupling area may be from 0.1to 0.3 mm, 0.1 to 0.5 mm, 0.3 to 0.5 mm, 0.5 to 3 mm, 0.5 to 2 mm, from1 to 3 mm, from 1 to 2 mm, from 0.5 to 2.5 mm, from 1.0 to 2.5 mm, from1.0 mm to 1.5 mm or 1.5 mm to 2 mm or any range formed by any of thesevalues. Values outside these ranges are also possible. Similarly,dimension e.g. length, L, along another direction of the coupling areamay be from 0.1 to 0.3 mm, 0.1 to 0.5 mm, 0.3 to 0.5 mm, 0.5 to 3 mm,0.5 to 2 mm, from 1 to 3 mm, from 1 to 2 mm, from 0.5 to 2.5 mm, from1.0 to 2.5 mm, from 1.0 mm to 1.5 mm or 1.5 mm to 2 mm or any rangeformed by any of these values. Values outside these ranges are alsopossible. These two directions may be orthogonal in someimplementations. The dimensions along the two directions need not be thesame. Accordingly, the coupling area may be symmetrical or asymmetrical.For example the aspect ratio of the coupling area (e.g., as measured bythe ratio of the length, L, to thickness, T, where length can be eitherthe resultant displacement from one end to another or the path lengthsuch as the arc length, P) may be from 1 to 2, from 1 to 1.75, from 1 to1.5, from 1 to 1.3, from 1 to 1.2, from 1 to 1.1 or any range formed byany of these values. Values outside these ranges are also possible. Asstated above, the dimension referred to herein such as thickness, T,length, L, path length P, may be single measurements, averages, maximumsor minimums.

As discussed above, different shapes and sizes of the coupling area arepossible. FIGS. 30A and 30B show a coupling optical element 2120 forcoupling light into the waveguide 2102 having a non-arcuate slit-shapedcoupling area. In particular, the coupling optical element 2120 has astraight slit coupling area. The slit is rectangularly shaped. Incontrast, the outcoupling optical element 2112 comprises a pinhole sizecoupling area similar to that shown in FIGS. 28A and 28B as well asFIGS. 29A and 29B.

As discussed above, a slit may be advantageous in being larger than apinhole and therefore collect more light. However, the narrowness of theslit provides a similar effect as a pinhole. For example, the reducedthickness, T, of the coupling area may remove multiple images from beingcollected by the coupling optical element 2120. Ghost images and/or blurcan thereby be reduced. As illustrated in FIG. 30A, the coupling area ofthe coupling optical element 2120 may have a length, L, and thickness,T. The thickness, T, may be about 1.0 mm or 1.5 mm in certainimplementations. The pinhole size thickness, T, of the coupling opticalelement 2120 for coupling light from an object such as the eye or anobject in the environment in front of the user and the eyewear has aneffect similar to that of a pinhole camera on the collection of lightand resultant imaging. The reduced size of the coupling area of thecoupling optical element 2120 is akin to the reduce size of a pinholecamera aperture. The result is that a large depth of focus or depth offield is provided without the need for a lens. The coupling opticalelement 2120 also need not have optical power nor does a lens need to beprovided at the coupling optical element 2120. Nevertheless, a largerange of object distances are in focus with such a design.

The out-coupling optical element 2112 shown in FIGS. 30A and 30B forcoupling light out of the waveguide to a camera is also of reduced size.In this particular implementation, the size and shape of theout-coupling optical element 2112 are similar or the same as thatdescribed above in connection with FIGS. 28A and 28B and 29A and 29B.The out-coupling optical element 2112, for example, may also be 1.5×1.5mm.

As discussed above, the coupling optical element 2120 and theout-coupling optical element 2112 may comprise diffractive opticalelements such as diffraction gratings. The coupling optical element 2120and the out-coupling optical element 2112 may comprise holograms orholographic optical elements. As discussed herein, the coupling opticalelement 2120 and the out-coupling optical element 2112 may compriseliquid crystal, liquid crystal gratings, polarization gratings, liquidcrystal polarization gratings or any combination thereof. The couplingoptical element 2120 may be configured to receive light (e.g., from theeye of the user or from the environment in front of the user) and coupleat least a portion of that light into the waveguide 2102. The couplingoptical element 2120 may also be configured to turn and direct a portionof the light to the out-coupling optical element 2112. The out-couplingoptical element 2112 may be configured to couple light received from thecoupling optical element 2120 and guided within the waveguide 2102 tothe out-coupling optical element 2112 out of the waveguide, for example,to a camera. In the configuration shown, a light consolidating opticalelement such as described above is not included.

As illustrated, the shape of the coupling area of the coupling opticalelement 2120 and the out-coupling optical element 2112 may vary. Asdiscussed above, in theory, a curved slit may potentially facilitatedirecting the light from the coupling optical element 2120 to theout-coupling optical element. However, a non-arcuate slit can also beused. A straight slit or a rectangular slit such as shown in FIGS. 30Aand 30B can direct sufficient light to the outcoupling optical element2112 so as to capture images with the camera. Nevertheless, othervariations in the shape are possible. For example, the edges of the slitmay be rounded.

The size of the coupling area may also be different. For example, theshorter dimension, the thickness, T, along one direction of the couplingarea may be from 0.1 to 0.3 mm, 0.1 to 0.5 mm, 0.3 to 0.5 mm, 0.5 to 3mm, 0.5 to 2 mm, from 1 to 3 mm, from 1 to 2 mm, from 0.5 to 2.5 mm,from 1.0 to 2.5 mm, from 1.0 mm to 1.5 mm or 1.5 mm to 2 mm or any rangeformed by any of these values. Values outside these ranges are alsopossible. This dimension, the thickness, T, may be smaller than theother dimension, the length, L. The other dimension, length, L, maycorrespond to the length or resultant displacement from one end toanother. As discussed above, alternately, a path length, P, may be usedto provide a measure of the larger dimension of the coupling area. Inthis example, where the slit is straight, the length, L, as measured bythe displacement from one end to another is the same as the path length,P. In some implementations, the length, L, or path length or arc length,P, may be from 1 to 5 mm, 1 to 3 mm, 5 mm to 40 mm, 10 to 40 mm, from 10to 30 mm, from 15 to 30 mm, from 15 to 25 mm, or any range formed by anyof these values. Values outside these ranges are also possible. Asdiscussed, these two directions may be orthogonal in someimplementations such as for the straight or rectangular slit, however,the directions need not be orthogonal. The slit is asymmetric. Forexample, the aspect ratio of the coupling area (e.g., as measured by theratio of the length, L, to thickness, T, where length can be either theresultant displacement from one end to another or the path length suchas the arc length, P) may be from 5 to 100, from 10 to 100, from 15 to100, from 20 to 100, from 10 to 40, from 10 to 50 or any range formed byany of these values. Values outside these ranges are also possible. Asstated above, the dimensions referred to herein such as thickness, T,length, L, path length P, may be single measurements, averages,maximums, or minimums.

The shape and size of the out-coupling optical element 2112 may alsovary. For example, although the out-coupling optical element 2112 areshown as squares, the shapes of either or both may be different. Theshape of the coupling area may, for example, be circular or otherwiseround. The size of the coupling area may also be different. For example,the dimension, e.g. thickness, T, along one direction of the couplingarea may be from 0.1 to 0.3 mm, 0.1 to 0.5 mm, 0.3 to 0.5 mm, 0.5 to 3mm, 0.5 to 2 mm, from 1 to 3 mm, from 1 to 2 mm, from 0.5 to 2.5 mm,from 1.0 to 2.5 mm, from 1.0 mm to 1.5 mm or 1.5 mm to 2 mm or any rangeformed by any of these values. Values outside these ranges are alsopossible. Similarly, dimension e.g. length, L, along another directionof the coupling area may be from 0.1 to 0.3 mm, 0.1 to 0.5 mm 0.3 to 0.5mm, 0.5 to 3 mm, 0.5 to 2 mm, from 1 to 3 mm, from 1 to 2 mm, from 0.5to 2.5 mm, from 1.0 to 2.5 mm, from 1.0 mm to 1.5 mm or 1.5 mm to 2 mmor any range formed by any of these values. Values outside these rangesare also possible. These two directions may be orthogonal in someimplementations. The dimensions along the two directions need not be thesame. Accordingly, the coupling area may be symmetrical or asymmetrical.For example the aspect ratio of the coupling area (e.g., as measured bythe ratio of the length, L, to thickness, T, where length can be eitherthe resultant displacement from one end to another or the path lengthsuch as the arc length, P) may be from 1 to 2, from 1 to 1.75, from 1 to1.5, from 1 to 1.3, from 1 to 1.2, from 1 to 1.1 or any range formed byany of these values. Values outside these ranges are also possible. Thedimensions referred to herein such as thickness, T, length, L, pathlength P, may be single measurements, averages, maximums or minimums(e.g., average thickness, maximum thickness, average length, maximumlength).

FIG. 31 shows an eyepiece including a coupling optical element 2112 forcoupling light into the waveguide 2102 and an out-coupling opticalelement 2120 for coupling light out of the waveguide 2102 to a camerawherein the coupling optical element 2112 has a non-arcuate (e.g.straight rectangular) slit-shaped coupling area included together withan image content incoupling optical element 2104 for receiving lightfrom an image projector, a light distribution element 2108 for directinglight from the image content incoupling optical element 2104 to anout-coupling optical element 2110, and an out-coupling optical element2110 for coupling light guided within the waveguide to a user forviewing image content. In some implementations, the coupling opticalelement 2112 includes optical power or has a lens associated therewiththat provides optical power. This optical power may collimate light fromobjects at a particular distance, such as from the anterior surface ofthe eye (e.g., cornea) to facilitate image capture of that object (e.g.,glint on the cornea). The optical power the first coupling opticalelement 2112 a and/or a lens associated therewith, may correspond to afocal length in a range from about 15 to 25 mm, 10 to 40 mm or 10 to 50mm, 5 to 40 mm or 5 to 50 mm or any range between any of the distancevalues herein. Values outside these ranges are also possible.

The slit coupling optical element 2112 is displaced laterally from theout-coupling optical element 2110. In other embodiments such as shown inFIGS. 30A and 30B, the system 900 need not be included on an eyepiecewith such components for presenting images to a user.

FIGS. 32A and 32B show first and second coupling optical elements 2112a, 2112 b for coupling light into the waveguide 2102 and first andsecond out-coupling optical elements 2120 a, 2120 b for coupling lightout of the waveguide to a camera wherein the coupling optical elements2112 am 2112 b have non-arcuate (e.g. straight rectangular) slit-shapedcoupling areas. Such a configuration may be useful for imaging differentobjects simultaneously. In some implementations, for example, differentportions of the eye such as the retina and the cornea (or glint thereon)can be imaged with the pair of coupling optical elements 2112 a, 2112 b,the pair of out-coupling optical elements 2120 a, 2120 b and one or morecameras. In some implementations, the first coupling optical element2112 a has optical power or is associated with a lens while the secondcoupling optical element 2112 b does not have a similar optical power ora similar lens (e.g., has no optical power and no lens associatedtherewith). In some implementations, the second coupling optical element2112 b could have optical power and/or a lens associated therewith,however, total optical power of the second coupling optical element 2112b and/or any lens associated second coupling optical element is lessthan the optical power of the first coupling optical element and/or anylens associated with the first coupling optical element). As discussedabove, such a system 900 may be configured, for example, to image ananterior portion of the eye using the first coupling optical element2112 a and image the retina using the second coupling optical element2112 b. As discussed above, in some implementations, the eye isilluminated with light having a first polarization and the secondout-coupling optical element 2120 b is polarization selective or hasassociated therewith a polarizer configured to filter out light of thefirst polarization so as to remove reflections from the cornea such asglint from degrading images of the retina.

FIG. 33 shows the first and second coupling optical elements 2112 a,2112 b for coupling light into the waveguide 2102 and first and secondout-coupling optical elements 2120 a, 2120 b for coupling light out ofthe waveguide 2102 to a camera wherein the coupling optical elements2112 am 2112 b comprise a non-arcuate (e.g. straight rectangular)slit-shaped coupling area integrated on an eyepiece. The eyepiecefurther includes an image content incoupling optical element 2104 forreceiving light from an image projector, a light distribution element2108 for directing light from the incoupling optical element 2104 to anout-coupling optical element 2110 for coupling light guided within thewaveguide 2102 to a user for viewing image content. In other embodimentssuch as shown in FIGS. 32A and 32B, the system 900 need not be includedon a waveguide with such components 2104, 2108, 2110 for presentingimages to a user.

FIGS. 34A and 34B show first and second coupling optical elements 2112a, 2112 b for coupling light into the waveguide 2102 and first andsecond out-coupling optical elements 2120 a, 2120 b for coupling lightout of the waveguide to a camera wherein the coupling optical elements2112 a, 2112 b comprise a non-arcuate (e.g. straight rectangular)slit-shaped coupling area. Such a configuration may be useful forimaging different objects simultaneously. In some implementations, forexample, different portions of the eye such as the retina and the cornea(or glint thereon) can be imaged with the pair of coupling opticalelements 2112 a, 2112 b, the pair of out-coupling optical elements 2120a, 2120 b and one or more cameras. In some implementations, the firstcoupling optical element 2112 a has optical power or is associated witha lens while the second coupling optical element 2112 b does not have asimilar optical power or a similar lens (e.g., has no optical power andno lens associated therewith). In particular, as discussed above, insome implementations, the second coupling optical element 2112 b couldhave optical power and/or a lens associated therewith, however, totaloptical power of the second coupling optical element 2112 b and/or anylens associated second coupling optical element is less than the opticalpower of the first coupling optical element and/or any lens associatedwith the first coupling optical element). The optical power of the firstcoupling optical element 2112 a and/or a lens associated therewith, maycorrespond to a focal length in a range from about 15 to 25 mm, 10 to 30mm, 10 to 40 mm or 10 to 50 mm, 5 to 40 mm or 5 to 50 mm or any rangebetween any of the distance values herein. Values outside these rangesare also possible.

As discussed above, such a system 900 may be configured, for example, toimage an anterior portion of the eye using the first coupling opticalelement 2112 a and image the retina using the second coupling opticalelement 2112 b. As discussed above, in some implementations, the eye isilluminated with light having a first polarization and the secondout-coupling optical element 2120 b is polarization selective or hasassociated therewith a polarizer configured to filter out light of thefirst polarization so as to remove reflections from the cornea such asglint from degrading images of the retina. The arrangement shown inFIGS. 34A and 34B is different than that shown in FIGS. 32A and 32B. Thefirst and second coupling optical elements 2112 a, 2112 b and the firstand second out-coupling optical elements 2120 a, 2120 b are aligned onthe same axis.

FIG. 35 shows the first and second coupling optical elements 2112 a,2112 b for coupling light into the waveguide 2102 and first and secondout-coupling optical elements 2120 a, 2120 b for coupling light out ofthe waveguide 2102 to a camera similar to that shown in FIGS. 33A and33B. The coupling optical elements 2112 am 2112 b comprise non-arcuate(e.g. straight rectangular) slit-shaped coupling areas aligned along acommon axis and integrated on an eyepiece. The eyepiece further includesan image content incoupling optical element 2104 for receiving lightfrom an image projector, a light distribution element 2108 for directinglight from the image content incoupling optical element 2104 to anout-coupling optical element 2110 for coupling light guided within thewaveguide 2102 to a user for viewing image content. In otherimplementations, such as shown in FIGS. 34A and 34B, the system 900 neednot be included on a waveguide with such components 2104, 2108, 2110 forpresenting images to a user.

As discussed above, polarization techniques can be used to attenuate orremove light from the anterior surfaces (e.g., corneal surfaces) fromaffecting images formed by light collected by the second couplingoptical element 2112 b. For example, the eye can be illuminated withpolarized light having a first polarization and the camera can form animage using light from the second out-coupling optical element 2120 busing light of a second different polarization. For example, the secondout-coupling optical element 2112 b may be a polarization selectivecoupling element that selectively couples out light of the secondpolarization different than the first polarization. Additionally oralternatively, a polarizer 2140 that filters out the first polarization(e.g., selectively transmits the second polarization) may be includedbetween the second out-coupling optical element 2120 b and the camera920 as illustrated in FIG. 27 .

Such a configuration may be used to reduce unwanted reflections (e.g.,glint), such as from the cornea when imaging the retina. Reflection fromthe cornea will be specular. Accordingly, if light of the firstpolarization is incident on the cornea, the light reflected from thecornea will retain that first polarization. In contrast, the retina isdiffuse. If light of the first polarization is incident on the retina,the light reflected from the retina does not retain solely the firstpolarization. The diffuse reflection more likely results in unpolarizedlight. Accordingly, the second polarization, different from the firstpolarization will be present in the light reflected from the retina. Asa result, by forming images with light coupled out of the secondout-coupling optical element 2120 b using light of the secondpolarization, images of the retina will be obtained while images of thecornea or glint will be suppressed. Likewise, by illuminating with afirst polarization and imaging with a second different polarization, theretina can be image with reduced glare from the cornea.

Accordingly, in various implementations, polarization specific opticalfilters or polarization selective optical elements (e.g. couplinggratings) may be used to reduce unwanted reflected light from the eye210 (e.g., from the cornea). For example, unwanted light, glare, orglint may be reflected off the cornea that may saturate an imagecaptured by the camera. As discussed above, light reflected from thecornea may be specular and maintain its polarization. By contrast, lightreflected off the retina may be more diffusely reflected and may be lesshomogenously polarized. Likewise, a combination of polarizers may beused to remove some or most of the unwanted light reflected from thecornea. Initially polarized light can be used for illuminating the eyeof the user. In some designs, a polarized illumination source (e.g., thelight source) may be used. Additionally or alternatively, a firstpolarizer (e.g., a polarization specific optical filter or apolarization selective optical coupling element coupling illuminationlight into an illumination waveguide) may be positioned at the beginningof the optical path of the illumination source to provide initialpolarization of the light to the eye. A second polarizer (e.g., apolarization specific optical filter or polarization selective couplingelement) may be positioned at the optical path before the light entersthe camera. The second polarizer may be rotated at 90° from the firstpolarizer (e.g. the polarizers may be “crossed”). As a result, the eyewill be illuminated with the first polarization with some light of thefirst polarization reflected from the cornea. This light will not passthrough the crossed polarizer (that preferentially passes light of thesecond polarization) located proximal the camera. However, lightreflected from the retina will include the second polarization.Likewise, light diffusely reflected from the retina will pass throughthe polarizer 2140 proximal the camera and will enable an image of theretina to be captured by the camera. Thus, in such configurations,unwanted light received from the eye (e.g., from cornea) and enteringthe camera may be reduced or eliminated from the images captured usinglight from the second coupling optical element 2112 b. Otherconfigurations are possible. For example, a polarization selectivecoupling elements 2112 b and/or a polarization selective out-couplingoptical elements 2120 b may be used in addition or in alternative topolarizers such as the polarizer 2140 proximal the camera. Additionallyor alternatively, a polarized light source may be used for illumination(e.g., illuminating the eye). The effect may again be to reduce orremove unwanted light received from the eye (e.g., from cornea) beforeentering the imaging device 920.

As illustrated in FIG. 27 , in various implementations, such polarizersare not used in an optical path from the first coupling optical element2112 a and the camera or between the first out-coupling optical element2120 a and the camera. As a result, images of the cornea and glint maybe obtained from light coupled by the first coupling optical element2112 a into the waveguide and/or light coupled out of the waveguide fromthe first out-coupling optical element 2120 a. As discussed above, thisfirst coupling optical element 2112 a may have optical power or a lensassociated therewith that is specifically used to image the corneaand/or glint. Likewise, polarization selective coupling optical elements2112 a or polarization selective out-coupling optical element 2120 athat filter out light of the first polarization would not be used as thefirst coupling optical element 2112 a and out-coupling optical element2120 a, respectively. Additionally, polarizers 2140 between the couplingoptical element 2112 a and the camera 920 or between the out-couplingoptical element 2112 a and the camera 920 that filter out light of thefirst polarization would not be used.

Systems for Illuminating the Eye

As mentioned above, eye tracking can be a useful feature in augmentedand mixed reality technologies. Glint-based eye tracking systems canutilize the reflections of light off of the eye, e.g., the cornea,potentially to provide a determination of the gaze direction of the eye.Systems described herein may be configured to direct light to the eyefrom a light output that is relatively close to the eye. Having thelight output closer to the eye may reduce system level complexities ofthe glint based eye tracking system. However, placing a light output toonear to the eye may result in unwanted visual occlusion. The view of theenvironment in front of the wearer of the head mounted display may, forexample, be occluded by a light source if disposed in front of theviewer close to the eye. Therefore, in some embodiments, various systemsdescribed herein include a structure that is configured to be placed infront of the eye so as to provide eye illumination without substantiallyoccluding the viewer's field of view of the environment in front of thehead mounted display. For example, a thin layer of material that may betransparent can be disposed in front of the eye without excessive visualocclusion. A light output for directing light onto the eye, e.g., forglint based tracking, can be incorporated into the transparent layerthat is placed in front of the eye. As will be discussed below, forexample, an elongate light guide such as an optical fiber or optical rodmay be included in the transparent layer to output light to the eye. Insome implementations, the transparent layer itself may comprise a planarwaveguide for conveying light to the eye. Such configurations may reduceobstructions to the user's field of view.

The transparent layer can be included in a head mounted displayconfigured to project light to a user to display augmented reality imagecontent in a field of vision of the user. The head mounted display maycomprise a frame configured to be supported on the head of the user. Thetransparent layer may be supported on the frame and disposed at alocation in front of the user's eye when the user wears the head-mounteddisplay such that the transparent portion transmits light from anenvironment in front of the user to the user's eye to provide a view ofthe environment in front of the user.

As shown in FIG. 36A, the transparent layer 3602 may be included as partof a stacked waveguide assembly 260 similar to that shown in FIG. 6 .The layer 3602 is in front of the user's eye 210 such that light can bedirected onto the eye potentially from a relatively short distance fromthe eye. The transparent layer 3602, however, may be disposed at anynumber of positions within an eyepiece. For example, FIG. 36B, whichshows an eye eyepiece 950 similar to that shown in FIG. 10 , depicts thetransparent layer 3602 disposed on the opposite side of the waveguide940 as the eye 210. The waveguide 940, therefore, is between thetransparent layer 3602 and the eye 210. In many implementations,however, the waveguide 940 is sufficiently thin such that thetransparent layer 3602 and the light output associated therewith isnevertheless sufficiently close to the eye. As discussed above, thewaveguide 940 can be used to both project image content into the eye 210as well as collect light reflected from the eye 210 to image the eye ona camera 920. FIGS. 37A and 37B also show eyepieces 950, similar to theconfigurations shown in FIG. 16 , including a waveguide 940 forcollecting light reflected from the eye to obtain images the eye. Theeyepiece 950, however, further comprises a transparent layer 3602configured to direct light to the eye 210. In the design shown in FIG.37A, the transparent layer 3602 is disposed rearward of the waveguide940 (e.g., closer to the eye 210) and is thus between the waveguide andthe eye. Alternatively, FIG. 37B illustrates the transparent layer 3602disposed forward the waveguide 940 (e.g., closer to the environment infront of the user) such that the waveguide is between the transparentlayer and the eye 210.

The transparent layer 3602 may comprise a material or combination ofmaterials that are transparent to visible light (e.g., glass, plastic).For example, the transparent layer 3602 may comprise a polymersubstrate, such as a polycarbonate layer. In some implementations, thetransparent layer 3602 comprises multiple sublayers stacked together.For example, the transparent layer 3602 may comprise an inner regionsandwiched between outer regions forward and rearward of the innerregion. In some designs, for example, an inner light guiding region(e.g., UV cured adhesive) is disposed between sheets (e.g., of plasticor glass). In some implementations, the inner region comprises plasticand the outer regions may comprise glass. Other configurations, however,are possible.

FIGS. 38A-38B illustrate two views of an eye illumination system 3600comprising a transparent layer 3602 with elongate light guides 3610included therein for conveying and directing light to the eye. Theelongate light guide has a length, a width, and thickness where thelength is much longer than the width and/or thickness, for example, atleast 10 times as long, possibly 50 times, 100 times or more. In theexample of FIGS. 38A-38B, the elongate light guides 3610 compriseoptical fibers 3610 within the transparent layer 3602. As shown in FIG.38A, the elongate light guide 3610, in this case the optical fiber, hasa first end 3611 a and a second end 3611 b, the first end being disposedwithin the transparent layer 3602 and more centrally located than thesecond end. In this implementation, the second end 3611 b is disposed atthe perimeter or edge 3615 of the transparent layer 3602. The second end3611 b includes an input for receiving light, for example, from a lightsource 3606 such as an LED, laser, or another optical fiber or opticalcoupler. In some embodiments, the second end 3611 b may be physicallycoupled to the light source or may be physically coupled to an opticalcoupler, which may, in turn, be physically coupled to the light source.In some implementations, the optical fiber may be relatively long or mayextend outward beyond the surface of the transparent layer such that thesecond end 3611 b may be substantially displaced from the transparentlayer. In some of these implementations, two or more optical fibers maybe routed to a same or common light source. The first end 3611 a of theoptical fiber 3610 may have an output for emitting light such that thelight is directed to the eye 210. The light output may comprise arelatively small aperture, for example, the light output may have anaperture size between 5 μm and 160 μm (e.g., 9 μm, 50 μm, 62.5 μm, 100μm). Accordingly, in some implementations, the output of the opticalfiber 3610 at the first end may be treated as a point source.

FIG. 38A shows four elongate light guides 3610 (e.g., four opticalfibers) in the transparent layer 3602. In some implementations, theoptical fibers 3610 may be arranged so that the first ends 3611 a of theoptical fibers 3610 form four corners of a square or rectangular shape.However, the optical fibers 3610 may be arranged in any number ofconfigurations and the ends 3611 a, 3611 b may be disposed at anylocation. Additionally, the number of elongate light guides 3610 (e.g.,optical fibers) may be more or less than four. In some implementations,a lens or other optics may be included at the first end 3611 a, e.g., tocollimated the light. In some implementations, a diffuser may beincluded at the output to diffuse the light output from the first end3611 a of the fiber. As discussed above, in various implementations, theplurality of elongate light guides (optical fibers) 3610 may haveoutputs that create point sources illuminating the eye 210. For example,as illustrated in inset 3650 of FIG. 38A, a set of four elongate lightguides (e.g. optical fibers) 3610 in a transparent layer 3602 havingfour respective outputs may form a square pattern of outputs (e.g.bright spots, point sources) 3612. As discussed above, the number and/orarrangement of the outputs, however, may be different.

As discussed above, one or more elongate light guide 3610 may compriseone or more optical fibers. The optical fiber 3610 may comprise a coreand cladding that surrounds the core. Light can be guided within thecore via total internal reflection off the cladding. The optical fiber3610 may comprise a single-mode or multi-mode optical fiber. The opticalfiber 3610 may have a core diameter have a range of, for example,between about 8 μm and 110 μm such as, e.g., approximately 9 μm, 50 μm,62.5 μm, or 100 μm. The optical fiber 3610 may comprise material that istransparent to visible light and in some implementations index matchingmaterial may be included around the optical fiber to reduce reflectionfrom the optical fiber. Accordingly, when the user views the environmentin front of the head mounted display device through the transparentlayer 3602, the optical fiber 3610 may obstruct vision to a relativelyminor extent.

In various implementations, the elongate light guides 3610 are embeddedin the transparent layer 3602. Additionally, as discussed above, thetransparent layer 3602 may comprise multiple layers in certain designs.FIG. 38B, for example, shows the transparent layer 3602 comprising aplurality of layers, namely, a pair of outer layers or regions 3616 onopposite sides of an inner layer or region 3618. In particular, thetransparent layer 3602 may comprise a pair of transparent covers 3616and transparent material in which elongate light guides (e.g., opticalfibers) 3610 are embedded. The transparent material comprising the innerregion 3618 is sandwiched between the transparent covers 3616. Thetransparent covers 3616 may comprise a material that is transparent tovisible light (e.g., glass, plastic) and may comprise sheets thatprovide mechanical support, for example, during and/or aftermanufacturing in certain cases. The transparent material comprising theinner region 3618 may comprise material that is also transparent tovisible light and that may provide index matching to the optical fiber(e.g., with the cladding of the optical fiber) and/or with the covers toreduce reflection and obscuration of the view of the eye. In someimplementations, this material in the inner region 3618 comprises aliquid or gel, possibly an adhesive, during the manufacture stage. Theliquid, gel, or adhesive, may solidify prior to use of the eyeillumination system 3600. The material in the inner region 3618 in whichthe elongate light guide (e.g., optical fiber) 3610 is embedded may becured to transform the material, for example, into a stronger, or moresolid, rigid, or stable structure. This material may comprise, forexample, a curable adhesive such as a UV curable adhesive. The elongatelight guide 3610 may be disposed between the covers 3616 in the curablematerial, and the material may be cured or otherwise solidified,hardened, or stabilized to fix the elongate light guide in place in thetransparent layer 3602. Other methods of fabricating the device,however, are possible.

In various implementations, a reflecting or light deflecting surface orelement 3620 is provided at the first end 3611 a of the elongate lightguide 3610 to eject light out of the elongate light guide 3610 towardthe user's eye. FIG. 38B, for example shows, the first end 3611 a of theelongate light guide (e.g. optical fiber) 3610 has a reflective surfaceor reflector 3620 configured to couple light through the output of saidoptical fiber 3610 in a particular direction. In particular, thereflective surface or reflector 3620 may be positioned at an angle withrespect to the length of the elongate waveguide guide 3610 and/or withrespect to the front and/or rear surfaces 3602 a, 3602 b of thetransparent layer 3602. The angled reflector 3620 may reflect incidentlight 3608 that is guided within the optical fiber 3610 from a lightsource 3606 towards the eye 210. In some implementations such as shownin FIG. 38B, the reflective surface or reflector 3620 may be angled todirect light out through the rear surface 3602 b of the transparentlayer 3602 toward the user's eye. The angled reflector 3620 may comprisean angled end 3626 of the elongate light guide 3610 such as an angledend of the optical fiber. For example, the angled reflector 3620 maycomprise a cleaved or beveled surface at the first end 3611 a of saidoptical fiber 3610. The angled surface 3626 of the optical fiber 3610may have an angle between 35 and 55 degrees (e.g., 45 degrees) withrespect to the length of the optical fiber 3610 that extends along thelength of the transparent layer 3602. The angled end surface 3626 of theoptical fiber 3610 may be polished in some implementations. The angledreflector 3620 may additionally comprise a reflective coating 3624 toincrease reflectivity. For example, the reflective coating 3624 maycomprise metal or other type of coating that increases the efficiency ofthe reflection of incident light 3608 off of the angled reflector 3620.This reflective coating 3624 may be disposed on to the angled surface3626 as shown in FIG. 38B. In some embodiments, a diffuser may be usedat the angled end 3626 of the elongate light guide 3610 or the end ofthe elongate light guide may otherwise be configured to diffuse thelight exiting therefrom. A diffuser may, in some cases, advantageouslyincrease the output cone angle of the light 3608 out of the transparentlayer 3602 towards the eye 210.

As discussed above, the elongate light guide 3610 may comprise opticalfibers as shown in FIGS. 38A-38B, however, the elongate light guide 3610may comprise other types of light guides or light pipes. For example,FIG. 39 illustrates a perspective view of an eye illumination system3600 employing at least one optical rod 3640 embedded in a transparentlayer 3602. The optical rod 3640 may comprise a material whose index ofrefraction is different from the surrounding waveguide such that lightmay be guided therein along the length of the optical rod 3640 by totalinternal reflection. This material may be transparent to visible lightand may comprise, for example, glass or plastic in some designs. Asdiscussed above, the elongate light guide, in this case an optical rod3640, has a length and a width and thickness where the length is muchlonger than the width and/or thickness, for example, at least 10 timesas long, possibly 50 times, 100 times, 150 times, 200 times or more orany range formed by any of these values. In some implementations, anoptical rod 3640 may be more rigid than an optical fiber. In someimplementations, the rod 3640 may be larger (wider or thicker) than thecore of an optical fiber. The optical rod 3640 may comprise any numberof shapes. The rod 3640 may, for example, comprise a cylindrical shapesuch as a right circular cylinder or a rectangular prism. Accordingly,for some designs, the rod may have a circular or rectangularcross-section perpendicular to its length. Other shapes are possible.For example, the rod 3640 may be conical in some cases. The width and/orthickness of the rod 3640 may be from 50 μm to 400 μm or 250 μm to 350μm (e.g., 300 μm) or any range between any of these values. Thedimensions (e.g., width and/or thickness) of the rod 3640 may be outsidethese ranges as well.

FIG. 39 shows the optical rod 3640 having first end 3611 a that isembedded in transparent layer 3602. In some implementations, the rod3640 comprises material having a higher index than the materialcomprising the transparent layer 3602. This configuration may causelight to be guided within the rod 3640. The light reflects off sidewallsof the rod 3640 as a result of totally internally reflection at theinterface between the high index rod and the lower index material of thetransparent layer 3602. Other configurations, however, may be employed.

Also as shown in FIG. 39 , the rod 3640 may have a reflective surface orreflector 3642 configured to direct light out of the rod at an anglewith respect to the length of the rod. In various implementations suchas shown, this reflector 3642 may be angled with respect to the lengthof the optical rod 3640 and/or the front and/or rear surfaces 3602 a,3602 b of the transparent layer 3602. In particular, the reflector 3642may comprise an angled surface that may be configured to reflect light3608 from a light source 3606 that is guided within the optical rod 3640towards the eye 210. For example, the angled surface may comprise abeveled surface at the first end 3611 a of the optical rod 3640. Theangled surface may comprise a surface with an angle between 35 and 55degrees (e.g. 45 degrees) with respect to the length of the optical rod3640 that extends along the length of the transparent layer 3602. Invarious implementations, a reflective coating may be applied to theangled end. The reflective coating may comprise metal or other type ofcoating that increases the efficiency of reflection of the incidentlight 3608 off of the angled reflector 3642 out of the transparent layer3602. As discussed above, in some implementations, a diffuser can beincluded at the first end 3611 a of the optical rod 3640, for example,possibly to increase the output cone angle of the light directed towardsthe eye 210.

As discussed above, the elongate light guide such as the optical rod3640 may be embedded in transparent layer 3602. The optical rod 3640may, for example, be embedded in transparent material within thetransparent layer 3602. In some implementations, for instance, thematerial in the inner region in which the elongate light guide (e.g.,rod) 3640 is embedded may be cured to transform the material, forexample, into a stronger, or more solid, rigid, or stable structure thatsolidifies, hardens, and/or stabilizes to fix the rod in place in thetransparent layer 3602.

In other implementations, the elongate light guide (e.g., rod) 3640 maybe disposed within a channel or cavity of the transparent layer 3602.The transparent layer 3602 may, for example, have a channel or cavitydesigned to accept or house the elongate light guide 3640. The channelor cavity may be larger than the diameter or width of the elongate lightguide 3640. For example, the elongate light guide 3640 may be arectangular prism with a width or height of 150 μm and the transparentlayer 3602 may have a channel or cavity with a width or height of 200μm. The elongate light guide may be secured in the channel or cavitywith a transparent material within the channel or cavity. Other methodsof fabricating the device, however, are possible.

As shown in FIG. 39 , at least one optical rod 3640 may be included inthe transparent layer 3602. Although four such rods 3640 are shown, moreor less rods may be employed. In some embodiments, the optical rod 3640may be placed within the transparent layer 3602 so that the first ends3611 a of the optical rod 3640 form four corners of a square or arectangle. However, the optical rod 3640 may be placed in any number ofarrangements or configurations within the transparent layer 3602.

The first end of the at least one optical rod 3640 may comprise anoutput that creates a point source illuminating the eye 210. Likewise,the plurality of optical rods 3640 may each have outputs that createpoint sources illuminating the eye 210. For example, as illustrated ininset 3652 of FIG. 39 , a set of four optical rod 3640 embedded in atransparent layer 3602 may create a square pattern of outputs (e.g.,bright spots, point sources) 3612. Other patterns, however, may be used.Such arrangements may be useful in eye tracking or estimation of thelocation, dimensions, or other characteristics of anatomical features ofthe user's eye such as the center of curvature of the cornea.

Accordingly, as discussed above, the transparent layer 3602 may includea plurality of optical outputs 3612. These optical outputs 3612 maycomprise the optical output of elongate light guides 3610, 3640 such asthe outputs of optical fibers or optical rods. These optical outputs3612 may have a height and/or width of between 5 μm and 600 μm. Forexample, these optical outputs 3612 may have a height and/or width ofbetween 5 μm and 160 μm (e.g., 9 μm, 35 μm, 50 μm, 62.5 μm, or 100 μm),160 μm and 600 μm (e.g., 200 μm, 300 μm, or 400 μm), or any rangebetween any of these values. The dimensions (e.g., width and/orthickness) of the elongate light guide (e.g., fibers, rods) 3610, 3640may be outside these ranges as well. Angled reflective surfaces may, inpart, establish the dimensions of the optical outputs 3612. As discussedabove, the angled reflective surface may comprise an angled cleavedoptical fiber, an engineered optical rod, or other angled surface. Theangled reflective surface may be disposed in the transparent layer.

The light may be provided by one or more light sources 3606 opticallyconnected to the elongate light guides 3610, 3640. The one or more lightsources 3606 may comprise one or more infrared light sources. The one ormore light sources 3606 may comprise one or more light emitting diodes(LEDs) or lasers. Other types of light sources 3606 may possibly beused. In some implementations, the one or more light sources 3606 mayhave outputs that are disposed at or proximal to the edge 3615 of thetransparent layer 3602 to couple light therein.

The transparent layer 3602 may, however, be configured differently todirect light to the user's eye. FIGS. 40A-40E, for example, illustratevariants, eye illumination systems 3600 employing at least one tiltedreflective surface 3630 embedded in a transparent layer 3602 to directlight out of the transparent layer to the eye. The transparent layer3602 may comprise at least one tilted reflective surface 3630 includedtherein to receive light guided, for example, by total internalreflection within the transparent layer. The at least one tiltedreflective surface 3630 may be angled such that light guided within thetransparent layer 3602 is reflected from the tilted surface 3630 anddirected through the rear major surface 3602 b out of the transparentlayer 3602 to the eye 210.

The transparent layer 3602 may comprise a plurality of waveguide regionsor optical channels 3632, 3636 therein that receive light from one ormore light sources 3606 and guide light from the light source within thewaveguide regions by total internal reflection. The waveguide regions3632, 3636 may, for example, comprise optically transparent materialhaving an index of refraction higher than that surrounding the waveguideregion such the light is reflected from sidewalls of the waveguideregions by total internal reflection. Additionally, the waveguideregions 3632, 3636 may include tilted reflective surfaces 3630 thatdeflect the light guided within the waveguide region out, for example,the rear surface 3602 b of the transparent layer 3602 toward the eye.

For example, as illustrated in FIGS. 40A, which is a cross-sectionthrough an example transparent layer 3602, the transparent layer maycomprise a set of regions: first and second waveguide regions 3632,3636, and a third transparent region 3634 therebetween. The firstwaveguide region 3632 has a first tilted (e.g., inclined) reflectivesurface 3630 and the second waveguide region 3636 has a second tilted(e.g., inclined) reflective surface 3630. The third transparent region3634 can also have first and second counter-part tilted (e.g., declined)surfaces. In some implementations, the inclined reflective surfaces 3630of the first and second waveguide regions 3632, 3636 abut the first andsecond counterpart declined surfaces of the third transparent region3634. In some implementations, one or more intervening layers may beincluded between the first waveguide region 3632 and the thirdtransparent region 3634 as well as between the second waveguide region3636 and the third transparent region. For example, the one or moreintervening layers may include a tilted surface 3630. The tilted surface3630 may comprise a reflective coating. For example, the reflectivecoating may be an IR-reflective coating. For example, the reflectivecoating may be a metallization. In some embodiments, the tilted surface3630 may be transparent to some or all of the visible spectrum. Invarious implementations, the first and second waveguide regions 3632,3636 and the third transparent region 3634 comprise a material ormaterials that are transparent to visible light such as glass orplastic. In various implementations, the first and second waveguideregions 3632, 3636 may comprise material having a refractive index suchthat light may be guided therein by total internal reflection betweenmajor surfaces.

FIGS. 40B and 40C are perspective and top views of an exampletransparent layer 3202 showing at least one light source 3606 disposedwith respect to at least one edge 3515 of the transparent layer suchthat light 3608 from the at least one light source 3606 is injected intothe at least one transparent layer, e.g., into the first and secondwaveguide regions 3632, 3636. Light 3608 may propagate through first andsecond waveguide regions 3632, 3636, be incident on a tilted surfaces3630 and reflected therefrom through the rear surface 3602 b and towardthe eye 210. The tilted reflective surface 3630 may comprise a surfacethat is angled with respect to a major surface (e.g., front and rearsurfaces 3602 a, 3602 b) of the transparent layer 3602. The tiltedsurface 3630 may be angled such that light 3608 guided within thetransparent layer 3602 is reflected from the tilted surface 3630 anddirected through a major surface (e.g., rear surface 3602 b) of thetransparent layer 3602 towards the eye 210. For example, the tiltedsurface 3630 may comprise a surface that forms an angle between 35 and55 degrees (e.g., 45 degrees) with respect to a major surface of thetransparent layer 3602. The tilted surface 3630 may comprise a polishedsurface. A reflective coating may be applied to portions of the tiltedsurface 3630. The reflective coating may comprise metal or other coatingthat increases the efficiency of reflection of light propagated throughthe waveguide or set of waveguides. In some embodiments, the reflectivecoating may be an IR reflective coating. As illustrated in the top viewshown in FIG. 40C, the tilted reflective surface 3630 is orientedvertically (e.g., extends superiorly-inferiorly) with respect to thehead mounded display and the user's head as opposed, for example, toextending horizontally (e.g., nasally-temporally) and having lightsources on the upper and lower edges 3615.

As shown, the at least one light source 3606 may comprise a plurality ofspaced apart light sources 3606 such as lasers and/or LEDs disposed atthe edge 3615 of the transparent layer 3602. In some implementations,reflection of light output from the discrete light sources 3606 off thetilted reflective surface 3630 may create a plurality of outputs 3612(possibly corresponding to point sources) illuminating the eye 210.Accordingly, the geometry (e.g., shape, orientation) of the at least onetilted reflective surface 3630 may affect the resultant arrangementand/or location of the outputs 3612 (e.g., point source(s)). Forexample, as illustrated in the inset 3654A of FIG. 40C, the two tiltedsurfaces 3630 embedded in a transparent layer 3602 (also shown in FIGS.40A and 40B) may create a square arrangement of outputs (e.g., brightspots, point sources) 3612 when paired with the set of four lightsources 3606 shown. A similar pattern of reflections or glints may beobserved on the eye. Variation in the number and/or position of thelight sources 3606 may alter the arrangement. For example, the patternof outputs (e.g., point sources) and corresponding reflection off theeye (e.g., glints) may be rectangular, triangular, or otherwise,depending possibly on the location and number of light sources.

Variations in the number, shape, position, and/or orientation of the atleast one tilted reflective surfaces 3630 are also possible. Forexample, although two tilted reflective surfaces 3630 are shown in FIGS.40B and 40C, only one tilted surface may be employed in someimplementations. The light sources 3606 may be included on only one sideof the transparent layer 3602 in such an example design. As anotherexample, the orientations (with respect to the vertical and horizontaldirections) of the tilted reflective surface 3630 may be different.Moreover, the orientations (with respect to the vertical and horizontaldirections) need not be the same for different tilted reflectivesurfaces included in a single transparent layer 3602. FIG. 40D, forexample shows a transparent layer 3602 including a pair of tiltedreflective surfaces 3630 oriented at an angle (e.g., by +15 and −15degrees) with respect to the vertical direction of the head mounteddisplay and head of the user. Two light sources 3606 are disposed onopposite sides of the transparent layer 3602 in the example shown. Theorientation of the tilted reflective surfaces 3630 with respect to thevertical of the head mounded display and the user's head is such that anupper pair of the resultant outputs (e.g., bright spots, point sources,etc.) 3612 may be farther apart than a lower pair of outputs (e.g.,bright spots, point sources, etc.) as illustrated in the inset 3654B ofFIG. 40D. A similar pattern of reflections or glints may be observed onthe eye. Although four light sources 3606 are shown, more or less lightsources and hence outputs (e.g., bright spots, point sources, etc.) 3612may be employed. Similarly, the number of light sources 3606 on eachside of the transparent layer 3602 need not be the same. Additionally,the tilted reflective surfaces 3630 may be oriented differently withrespect to the vertical of the head mounted display and the user's head.Any angle from horizontal to vertical may be possible. In anotherexample, a hexagonal pattern of outputs (e.g., bright spots, pointsource, etc.) 3612 may be created by having a hexagonal arrangement oftilted reflective surfaces 3630 such as shown in FIG. 40E and therespective inset 3654C. A similar pattern of reflections or glints maybe observed on the eye. As illustrated, six light sources 3606 are used,three on each side of the transparent layer 3602. A hexagonal pattern ofoutputs (e.g., bright spots, point sources) 3612 may also be produced byanother configuration of tilted reflective surfaces 3630 illustrated bythe top view of the transparent layer 3602 shown in FIG. 40F. Again, sixlight sources 3606 are used. The lateral (e.g., nasal versus temporal)position of the tilted reflective surfaces 3630 may result in theoutputs (e.g., bright spots, point sources, etc.) 3612 produced by thelight sources 3606 being displaced with respect to each other causingthe laterally displaced light outputs (e.g., bright spots, pointsources, etc.) 3612 shown in the inset 3654D of FIG. 40F. Again, similarpattern of reflections or glints may be observed on the eye.

As discussed above, the tilted reflective surfaces 3630 may be orienteddifferently with respect to the vertical and horizontal. For example,instead of the tilted reflected surfaces 3630 being vertical, the tiltedreflective surfaces may be horizontal in some designs. In such cases,the light sources 3606 may be included on the upper and/or lower sidesof the transparent layer 3602.

In any of the design discussed herein, a light source 3606 may beoptically coupled to the transparent layer 3602 thereby injecting lighttherein. One or more optical coupling element, for example, lens orother optics may be used in various implementations. The light source3606 may be configured to emit a wavelength or band of wavelengths oflight, which may include invisible (e.g. infrared, near infrared, etc.)or visible light.

As described herein, the eye illumination system 3600 may be used totransmit light 3608 towards the eye 210 such that the light reflectedoff of the angled reflector 3620 of the optical fiber 3610, angledreflector 3642 of the optical rod 3640, or tilted reflective surface3630 of the waveguide regions or optical channels may producereflections off the cornea of the eye 210. In some cases, the light fromthe transparent layer 3602 corresponds to point sources. Similarly, thereflection 3612 off the cornea may comprise localized points or glints.The light reflected off of the cornea may then be received by a camera.In various implementations, by analyzing the corneal reflections, thegaze direction of the eye 210 may be determined.

Additional Configurations for Collecting Light

As described above, various configurations can permit light to becollected, for example, from the eye and be directed to a capture imagessuch as but not limited to video images. FIGS. 41A-41B, for example,show an eyepiece 4000 comprising one or more waveguides 4002. FIG. 41Bis a top or front view of the waveguide 4002 while FIG. 41A is a sidecross-sectional view through the eyepiece 4000 and/or waveguide 4002. Inthis example, only one waveguide 4002 is shown in the eyepiece 4000,however, the eyepiece can comprise one or more waveguides. A couplingoptical element 4004 (possibly referred to as an in-coupling grating,ICG, or in-coupling optical element in this context) is disposed on thewaveguide 4002 and is configured to couple light, for example, reflectedfrom the eye 4090 into the waveguide to be guided therein by totalinternal reflection. (This same coupling element may, in someimplementations, be configured to outcouple light from a projectorguided within the waveguide 4002 to the user's eye to present imagecontent to the user although this coupling element need not be soconfigured.) This coupling element 4004 may comprises a diffractiveoptical element such as a diffraction grating.

First and second light redirecting elements (also possibly referred toas orthogonal pupil expanders, OPEs) are shown. The first and secondlight redirecting elements 4006, 4008 comprise diffractive opticalelement having diffractive features. The first and second lightredirecting elements 4006, 4008 may comprise, for example, diffractiongratings such as one-dimensional (1D) diffraction gratings. See forexample FIG. 42 . An out-coupling area 4010 is also shown in FIGS. 41A,41B, and 42 . This out-coupling area 4010 is shown in FIGS. 41B and 42as square, however, other shapes are possible. The first and secondlight redirecting elements 4006, 4008 are disposed to receive lightguided within the waveguide 4002 from the coupling optical element 4004.The first and second light redirecting elements 4006, 4008 redirectlight from the coupling optical element 4004 to the out-coupling area4010. For example, light directed by the first light redirecting element4006 may propagate within the waveguide by total internal reflection tothe second light redirecting element 4008. When this light is incidenton the second light redirecting element 4008, this light or at least aportion thereof may be coupled out of the waveguide 4002. Similarly,light directed by the second light redirecting element 4008 maypropagate within the waveguide 4002 by total internal reflection to thefirst light redirecting element 4006. When this light is incident on thefirst light redirecting element 4006, this light or at least a portionthereof may be coupled out of the waveguide 4002. This light out-coupledfrom the first and second light redirecting elements 4006, 4008 (e.g.,proximal to the border therebetween) may be directed to a sensor orcamera. Accordingly, FIGS. 41A-41B and 42 show a sensor or camera 4012disposed with respect to the out-coupling area 4010 to receive lightcoupled out by diffractive features in the out-coupling area 4010.

The coupling element 4004 may comprise a grating such as a 1D grating insome implementations. In various implementations, the grating comprisingthe coupling optical element 4004 may have a grating vector 4018. Thisgrating vector 4018 may be orthogonal to the diffractive features ofthat grating. In some implementations, this grating may compriseelongate diffractive features having a length orthogonal the gratingvector 4018. In the example shown, the grating vector is parallel withan edge of the eyepiece and directed toward the first and second lightredirecting features 4006, 4008. This grating vector may be parallel toa centerline 4020 between the first and second light redirectingelements 4006, 4008 and/or to the border therebetween.

The first and second light redirecting optical elements 4006, 4008 canform an angle with respect to each other. This angle can, for example,be greater than 0° less and less than 180°. In some implementations,this angle can be greater than 75° less and less than 160°. In someimplementations, this angle can be about 120°. In some implementations,first and second light redirecting elements 4006, 4008 are angled withrespect to each other so as to form a chevron shape.

The first and second light redirecting elements 4006, 4008 may comprisediffractive features. For example, the first and second lightredirecting elements 4006, 4008 may each comprise a 1-D gratingstructure. In some implementations, each of the first and second lightredirecting elements 4006, 4008 has respective grating vectors 4014,4016 such as shown in FIG. 42 . This grating vector 4014, 4016 may beorthogonal to the diffractive features of that grating. For example, thediffractive features may comprise elongate features having a length thatis oriented orthogonal the grating vector 4014, 4016. In variousimplementations, the grating vector 4014, 4016 may be oriented at anangle such as about 60° with respect to the long edge of the eyepiece asshown in FIG. 42 or with respect to an axis or centerline 4020 that runsbetween the first and second light redirecting elements 4006, 4008 orwith respect to the border therebetween or with respect to the gratingvector 4018 of the coupling optical element 4004. In someimplementations, the grating vector 4014, 4016 of the first and/orsecond light redirecting element 4006, 4008 may be oriented at an angleof 60° with respect to the grating vector 4018 of the coupling opticalelement 4004.

Accordingly, in some implementations, the diffractive features of thefirst redirecting element 4006 and the diffractive features of thesecond redirecting element 4008 are oriented an angle with respect toeach other. The diffractive features of the first redirecting element4006 and the diffractive features of the second redirecting element 4008may, for example, be oriented an angle with respect to each other ofmore than 90° and less than 170°. This angle may, for example be 120° insome implementations.

In some implementations, the sum of the angles of the grating vectors4018, 4014, 4016 for the coupling optical element 4004 and the first andsecond light redirecting elements 4006, 4008 is less than 1°, ½°, ¼°, ⅛°or is zero or may be in any range formed by any of these values. As aresult, in some such embodiments, light input through the couplingoptical element 4004 so as to be guided in the waveguide 4002 that isredirected by the first redirecting optical element 4006 to the secondredirecting optical element 4008 is output out of the waveguide by thesecond redirecting optical element. Similarly, light input through thecoupling optical element 4004 so as to be guided in the waveguide 4002that is redirected by the second redirecting optical element 4008 to thefirst redirecting optical element 4006 is output out of the waveguide bythe first redirecting optical element.

A wide range of dimensions are possible. Some example dimensions for theparameters shown in FIG. 42 are listed below.

-   -   D_(EDGE), Margin to waveguide edge—5 mm    -   W_(ICG), Width of coupling optical element (ICG)—22 mm    -   L_(ICG), Length of coupling optical element (ICG)—22 mm    -   Direction of coupling optical element (ICG) Grating Vector is at        0° with respect to the eyepiece long-edge    -   W_(GAP)—Gap between coupling optical element (ICG) edge and        sensor center—25 mm    -   W_(OCG), Width of first and/or second light directing element        (OCG) Trapezium—12 mm    -   L_(OCG), Length of first and/or second light directing element        (OCG) Trapezium—16 mm    -   Direction of first and/or second light directing element (OCG)        Grating Vectors (θ) are at ±60° with respect to the eyepiece        long-edge as indicated    -   Angle of first and/or second light directing element (OCG)        Trapeziums (θ) are at ±60° with respect to Eyepiece long-edge as        indicated.

In this example, the coupling optical element (ICG) 4004 and both thefirst and second light redirecting optical element (OCGs) 4006, 4008have the same grating pitch. As an example for Infra-Red (IR) light at850 nm wavelength, the grating pitch can be 580 nm for maintaining TIRand providing reasonable field-of-view of the imaging system, e.g., afield-of-view of about 15° in both X and Y directions. Variations arepossible. The gratings may comprise liquid crystal. For liquid crystalgratings or diffractive optical elements (for example, liquid crystalpolarization gratings), as an example, the helical pitch and gratingthickness may be 0.66 μm and 0.8 μm for the coupling element (ICG), and1.7 μm and 0.9 μm, respectively, for each of the light redirectingelements (OCGs). The substrate or waveguide thickness may be chosen forcompact size, for example, to allow for enough bounces within thewaveguide. This thickness may, for example, be between 350 μm and 500μm.

Designs such as shown in FIG. 41A-41B or 42 , having first and secondlight redirecting optical elements 4006, 4008 may, for example, increasethe field-of-view of the imaging system.

Variations in the design are possible. FIG. 43A, for example, shows anout-coupling optical element 4022 for coupling light guided within thewaveguide out of the waveguide 4002. This out-coupling element 4022 maybe useful when a gap exists between the first and second lightredirecting elements 4006, 4008, e.g., at the border between the firstand second light redirecting elements. The border 4030, for example, maycomprise a space. If such a gap is present, some light coupled into thewaveguide 4002 from the at least one coupling element 4004 may not beincident on the first and second light redirecting elements 4006, 4008and instead pass directly through the gap therebetween. Positioning theout-coupling element 4022 to receive this light as shown in FIG. 43A maycause this light, which would otherwise pass through the gap between thefirst and second light redirecting elements, to be coupled out of thewaveguide 4002, for example, to the camera 4012. As illustrated in FIG.43A, this out-coupling element 4022 is disposed to receive light (e.g.,reflected from the eye 4090) that is in-coupled into the waveguide 4002by the at least one coupling element 4004. In particular, thisout-coupling element 4022 is disposed in an optical path between the atleast one coupling optical element 4004 and the border 4030 between thefirst and second light redirecting elements 4006, 4008 and the gaptherebetween to receive light (e.g., reflected from the eye 4090) thatis in-coupled into the waveguide 4002 by the at least one couplingelement 4004 that would otherwise pass through the gap. This light maytravel, for example, between the first and second light redirectingoptical element 4006, 4008. This light may travel, for example, along apath parallel to or along the centerline 4020.

This out-coupling element 4022 may comprise a grating having a gratingvector 4023, for example, parallel to the grating vector 4018 of the atleast one coupling element 4004 and/or parallel to the centerlinethrough the first and second light directing elements 4006, 4008 orborder 4030 therebetween. This out-coupling element 4022 is disposedbetween the coupling element 4004 and the first and second lightredirecting elements 4006, 4008. This out-coupling element 4022 iscloser to the first and second light redirecting elements 4006, 4008than the coupling element 4004. In the example shown, this out-couplingelement 4022 is shown near the border 4030 between the first and secondredirecting elements 4006, 4008 and along the centerline 4020 betweenthe first and second light redirecting element 4006, 4008. Thisout-coupling element 4022 is also shown adjacent to both the first andsecond light redirecting element 4006, 4008 and conforms to the shape ofthe first and second light redirecting elements. Accordingly, in thiscase this out-coupling element 4022 is triangular shaped, although othershapes are possible.

This out-coupling element 4022 couples light guided within the waveguide4002 out of the waveguide and to the camera 4012. As illustrated in FIG.43A, the out-coupling area 4010 and the camera 4012 are thus shifted tooverlap portions of the out-coupling optical element 4022. In variousimplementations, this out-coupling element 4022 couples out light guidedwithin the waveguide 4002 to the camera 4012 that would otherwise passthrough the gap between the first and second light redirecting elements2006, 2008 and that would not be coupled out to the camera to contributeto the field-of-view forward the eyepiece. This additional couplingelement 4022 near the border 4030 between the first and second lightredirecting elements 4006, 4008 captures field-of-view not obtained bythe first and second light redirecting element near the center of thecoupling element 4004.

FIG. 43B shows a border 4024 between the first and second lightredirecting optical elements 4006, 4008 that is not a single straightline (as is shown in FIG. 42 where the border 4024 is flat and/orstraight). In contrast, the border 4024 in FIG. 43B is undulating. Theborder 4024 in this case is a sawtooth pattern. Other shapes, however,are possible. This irregularly shaped border 4024 permits the first andsecond light redirecting elements 4006, 4008 to capture morefield-of-view, for example, field-of-view missed by having a gap betweenthe first and second light redirecting elements 4006, 4008.

As discussed above, if a gap is between the first and second lightredirecting elements, 4006, 4008, light coupled into the waveguide 4002by the coupling element 4004 may pass through the gap between the firstand second light redirecting elements 4006, 4008 and not be coupled outof the waveguide into the camera 4012. This may result in some of thefield not being imaged and captured by the camera 4012. For example, theimages produced by the camera 4012 may comprise a strip or band whereless (possible negligible or no) light is captured.

The shape of the first and second light redirecting elements 4006, 4008,and in particular, the shape of the border 4024 therebetween, may beconfigured to couple light out that would otherwise pass through a gapbetween the first and second light redirecting elements. The first lightredirecting element 4006 may, for example, include at least one regionthat extends past the most distal end of the second light redirectionelement 4008. For example, this region of the first light redirectingelement may extend further away from the center of the first lightredirecting element and closer to the center of the second lightredirecting element than a portion of the second light redirectingelement. Similarly, the second light redirecting element 4008 may, forexample, include at least one region that extends past the most distalend of the first light redirection element 4008. For example, thisregion of the second light redirecting element 4008 may extend furtheraway from the center of the second light redirecting element and closerto the center of the first light redirecting element than a portion ofthe first light redirecting element. The first and second lightredirecting elements can be said to be interlocking. The sawtoothpattern shown in FIG. 43B possesses this property. The tips of the teethof the first light redirecting element 4006 extend past and closer tothe center of the second light redirecting optical element than the tipsof the teeth of the second light redirecting element 4008, and viceversa. Accordingly, the teeth on the first light redirecting element4006 are interlocking with the teeth of the second light redirectingelement 4008. The first light redirecting element 4006 is interlockingwith the second light redirecting element 4008. This interlockingconfiguration enables light from the coupling optical element 4004 thatis guided within the waveguide 4002 that might otherwise pass through agap in a non-interlocking configuration to intersect either of first orsecond interlocking light redirection optical elements 4006, 4008 and becoupled out of the waveguide to the camera 4012. Another design in shownin FIG. 44 . This design shows a coupling optical element 4004 and anout-coupling optical element 4026. An optical path extends from thecoupling optical element 4004 and to the out-coupling optical element4026 without any intervening light redirection optical elements 4006,4008 or gratings. Light is coupled into the waveguide 4002 via thecoupling optical element 4004 and is guided within the waveguide bytotal internal reflection to the out-coupling optical element 4026. Theout-coupling optical element 4026 may be configured to couple lightguided within the waveguide 4002 from the coupling optical element 4004out of the waveguide and to the camera 4012. Either of both the couplingoptical element 4004 and the out-coupling optical element 4026 comprisediffractive optical elements or gratings and may comprise diffractivefeatures as describe herein. In some implementations, the sum of thegrating vectors for the coupling optical element 4004 and theout-coupling optical element 4026 is less than 1°, ½°, ¼°, or ⅛° and maybe zero or may be in any range between any of these values.

The coupling element(s) 4004, the out-coupling optical element 4022,4026 and light redirecting elements 4006, 4008 may be on the frontand/or back side of the waveguide 4002. In some implementations, thelight redirecting element(s) 4006, 4008 may be disposed on oppositesides of the waveguide. For example, the first light redirecting element4006 may be on the front side of the waveguide 4002 and the second lightredirecting element 4008 may be on the back side of the waveguide, orvice versa. In some designs, when the light redirecting element(s) 4006,4008 are on opposite sides of the waveguide, a region of the first lightredirecting element 4006 may overlap a region of the second lightredirecting element 4008. These regions of overlap may be located suchthat the center field of view can be captured. One or more of thecoupling element(s) 4004, the out-coupling optical element 4022, 4026and light redirecting elements 4006, 4008 may comprise blazed gratings.In some implementations, blazed gratings may be used to preferentiallydirect light in one direction as opposed to another opposite direction.One or more (potentially all) of the coupling element(s) 4004, theout-coupling optical element 4022, 4026 and light redirecting elements4006, 4008 may comprise liquid crystal gratings such as liquid crystalpolarization gratings. Liquid crystal gratings may be more wavelengthspecific than other types of grating such as surface relieve grating.For such liquid crystal gratings, the diffraction efficiency is lower(possibly significantly lower) for other wavelengths than the designwavelength. Accordingly, the liquid crystal grating could be designed tooperate more on (e.g., diffract more) infrared light than on visible.The diffraction of visible light by such grating that causes orcontributes to a “rainbow” effect can thereby be reduced. The liquidcrystal gratings may comprise, for example, cholesteric liquid crystal,in some implementations.

In some implementations, however, the grating(s) or diffractive opticalelement(s) are formed by imprinting a material with a surface havingsurface relief, for example, imprinting with an imprint templatecomprising a plurality of features. Such imprinting will form surfacerelief features in the material. The plurality of features in theimprint template can comprise nanostructure in some cases. Accordingly,in certain implementations, the resultant surface relieve pattern cancomprise nanostructures. The material may or may not be cured afterimprinting. The surface relief features in the material may be used toform the grating or other diffractive optical element. Likewise, invarious implementations, one or more (possibly each) of the at least onecoupling optical element 4004, the first light redirecting opticalelement, the second light redirecting optical element 4008, and/or theout-coupling optical element 4022 are formed using imprint technology,e.g., imprinting a material to form surface relief therein, with saidfeatures possibly having nanometer scale sizes.

This system, for example, the diffractive optical elements (e.g., thegratings) may be configured to operate on infrared light in someimplementation. The pitch of the diffractive features or diffractiongratings may be designed for infrared. Images of the eye such as for eyetracking may be captured with the systems described herein. This systemmay image, for example, the cornea or the retina in some examples.

In some implementations, a part of or all of the at least one couplingoptical element 4004, the first light redirecting optical element 4006,or the second light redirecting optical element 4008, or any combinationthereof can be graded (e.g., varying) in diffractive properties. Suchgradation may, for example, increase (e.g., optimize in some instances)imaging properties such as efficiency and/or uniformity. In someexamples, the efficiency of the diffractive features or diffractiongratings changed, but with the pitch maintained. For some surface reliefgratings, the gradation in, for example, diffraction efficiency or othercharacteristic, may be achieved by changing the grating thickness and/orduty cycle. For some liquid crystal gratings, the gradation may beachieved by changing the grating thickness and/or the helical pitch.Other examples are possible.

EXAMPLES

A variety of example systems and methods are provided below. Any of thefollowing Examples or Additional Examples can be combined. Additionally,any of the following Examples or Additional Examples can be integratedwith a head mounted display. In addition, any of the following Examplesor Additional Examples can be implemented with a single depth planeand/or with one or more depth planes and/or one or more variable depthplanes (e.g., one or more elements with variable focusing power thatprovide accommodation cues that vary over time).

Example Section I

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   a camera;        -   at least one waveguide;        -   at least one coupling optical element configured such that            light is coupled into said waveguide and guided therein; and        -   at least one out-coupling element configured to couple light            guided within said waveguide out of said waveguide and            direct said light to said camera,        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light that is coupled into            said waveguide via the coupling element and guided therein            and that is coupled out from said waveguide by said            outcoupling coupling element such that images may be            captured by said camera.    -   2. The system of Example 1, wherein said at least one coupling        optical element is configured such that light from the        environment in front of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said environment may be        captured by said camera.    -   3. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said camera.    -   4. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said waveguide and guided therein        such that images of said eye may be captured by said camera,        said system configured to image an anterior portion of said eye.    -   5. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said waveguide and guided therein        such that images of said eye may be captured by said camera,        said system configured to image a corneal surface of said eye.    -   6. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said waveguide and guided therein        such that images of said eye may be captured by said camera,        said system configured to image the retina of said user's eye.    -   7. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   8. The system of Example 7, wherein said eyepiece is configured        to receive light from said image projector and to direct said        light into said user's eye to display augmented reality image        content to the user's vision field.    -   9. The system of any of Examples 7-8, wherein said eyepiece        comprises said at least one waveguide.    -   10. The system of any of Examples 7-9, wherein said image        projector is configured to direct light into an edge of said        eyepiece.    -   11. The system of Examples 9 or 10, wherein said image projector        is configured to direct light into an edge of said at least one        waveguide.    -   12. The system of any of the Examples above, further comprising        at least one in-coupling optical element configured to in-couple        light from said image projector into said at least one waveguide        so as to guide light from said image projector for providing        said image content to said user's eye.    -   13. The system of any of the Examples above, wherein said at        least one coupling optical element is also configured to couple        light from said image projector guided within said waveguide out        of said at least one waveguide such that image content can be        viewed by the user's eye.    -   14. The system of any of the Examples above, wherein the same        coupling optical element is configured to couple light from said        image projector guided within said waveguide out of said        waveguide such that image content can be viewed by the user's        eye and to couple light into said at least one waveguide to be        guided therein to said camera.    -   15. The system of any of Examples 1 to 12, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said        waveguide out of said at least one waveguide such that image        content can be viewed by the user's eye.    -   16. The system of any of the Examples above, wherein said at        least one coupling optical element faces the eye of the user        wearing the head mounted imaging system to receive light from        said eye.    -   17. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        from the environment in front of the user wearing the head        mounted imaging system is coupled into said at least one        waveguide and guided therein such that images of said        environment may be captured by said camera.    -   18. The system of any of the Examples above, wherein said at        least one coupling optical element faces the environment in        front of the user wearing the head mounted imaging system to        receive light from said environment.    -   19. The system of Example 15, wherein said at least one image        content out-coupling optical element configured to couple light        from said image projector guided within said waveguide out of        said at least one waveguide and said at least one coupling        optical element configured such that light is coupled into said        waveguide and guided therein to said camera are superimposed on        each other.    -   20. The system of Example 15, wherein said at least one image        content out-coupling optical element configured to couple light        from said image projector guided within said waveguide out of        said at least one waveguide and said at least one coupling        optical element configured such that light is coupled into said        waveguide and guided therein to said camera are stacked over the        other.    -   21. The system of Example 15, wherein said at least one image        content out-coupling optical element configured to couple light        from said image projector guided within said waveguide out of        said at least one waveguide and said at least one coupling        optical element configured such that light is coupled into said        waveguide and guided therein to said camera are integrated in        the same diffractive optical element.    -   22. The system of Example 15, wherein said at least one coupling        optical element is configured such that light is coupled into a        first waveguide and guided therein to said camera and said at        least one image content out-coupling optical element is        configured to couple light from said image projector guided        within a second waveguide out of said second waveguide.    -   23. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        is coupled into a first waveguide and guided therein to said        camera and said image projector is configured to couple light        into a second waveguide to provide image content to said eye.    -   24. The system of any of the Examples above, wherein said image        projector comprises a light source, a modulator, and projection        optics.    -   25. The system of any of the Examples above, wherein the image        projector comprises scanning optical fiber.    -   26. The system of any of Examples 24 or 25, wherein the        modulator comprises a light modulator.    -   27. The system of Example 26, wherein the light modulator        comprises a spatial light modulator.    -   28. The system of any of the Examples above, wherein said camera        comprises a detector array and imaging optics.    -   29. The system of Example 28, wherein said imaging optics is        configured to focus collimated light onto said detector array.    -   30. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        visible light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   31. The system of any of the Examples above, wherein said at        least one waveguide comprises a stack of waveguides.    -   32. The system of Example 31, wherein different waveguides of        the stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   33. The system of Example 31 or 32, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   34. The system of any of Examples 31, 32, or 33, wherein        different waveguides comprise first, second, and third        waveguides, said system is configured such that the first is for        red color light, the second for is green color light, and the        third is for blue color light.    -   35. The system of any of the Examples 12 to 34, wherein the        in-coupling optical element comprises a diffractive optical        element or reflector.    -   36. The system of any of the Examples 12 to 34, wherein the        in-coupling optical element comprises a diffractive optical        element.    -   37. The system of any of the Examples above, wherein the        coupling optical element comprises a diffractive optical        element.    -   38. The system of any of the Examples above, wherein the        coupling optical element comprises liquid crystal.    -   39. The system of any of the Examples above, wherein the        coupling optical element comprises a liquid crystal polarization        grating.    -   40. The system of any of the Examples above, wherein the        out-coupling optical element comprises a diffractive optical        element.    -   41. The system of any of the Examples above, wherein the        coupling optical element comprises liquid crystal.    -   42. The system of any of the Examples above, wherein the        coupling optical element comprises a liquid crystal polarization        grating.    -   43. The system of any of the Examples above, wherein the        coupling element is configured to increase a dimension of the        eyebox along at least one axis.    -   44. The system of Example 43, further comprising an orthogonal        pupil expander comprising at least one light redirecting element        in or on said at least one waveguide that is configured to        increase a dimension of an eyebox along an axis that is        orthogonal to the at least one axis.    -   45. The system of Example 44, wherein said at least one light        redirecting element comprises a diffractive optical element.    -   46. The system of any of the Examples above, wherein the same        coupling element is configured to (a) couple light into said at        least one waveguide to be received by said camera and to (b)        couple light from said image projector out from said at least        one waveguide to said user's eye.    -   47. The system of any of the Examples above, wherein the same        coupling element is configured to (a) couple light from said        environment into said at least one waveguide to be received by        said camera and to (b) couple light from said image projector        out from said at least one waveguide to said user's eye.    -   48. The system of any of the Examples above, wherein the same        coupling element is configured to (a) couple light from said eye        into said at least one waveguide to be received by said camera        and to (b) couple light from said image projector out from said        at least one waveguide to said user's eye.    -   49. The system of any of the above Examples, further comprising        a reflective surface having optical power disposed to receive        light reflected from the user's eye that passes through said        eyepiece and to direct said light back to said eyepiece.    -   50. The system of Example 49, wherein said at least one coupling        element is configured such that light from the user's eye that        passes through the at least one waveguide and is reflected from        the reflective surface back to the at least one waveguide is        coupled into said at least one waveguide and guided therein.    -   51. The system of any of Examples 49 to 50, wherein the camera        is disposed in an optical path with respect to said at least one        out-coupling optical element to receive at least a portion of        the light from the user's eye that is reflected from the        reflective surface and coupled into said waveguide via the        coupling element and guided therein and that is coupled out from        said waveguide by said outcoupling coupling element.    -   52. The system of any of Examples 49 to 51, wherein the        reflective surface reflects infrared light but transmits visible        light.    -   53. The system of any of Examples 49 to 52, wherein the        reflective surface is curved.    -   54. The system of any of Examples 49 to 53, wherein the        reflective surface is disposed on a curved optical element.    -   55. The system of any of Examples 49 to 54, wherein the        reflective surface is disposed on a concave mirror.    -   56. The system of any of Examples 49 to 55, wherein the        reflective surface has positive optical power in reflection and        negligible optical power in transmission.    -   57. The system any of Examples 49 to 56, wherein the reflective        surface is configured to collimated light from the user's eye.    -   58. The system of any of Examples 49 to 57, wherein the        reflective surface is configured to collimate light from the        retina of the user's eye.    -   59. The system of any of Examples 49 to 58, wherein the        reflective surface is configured to collimate light from an        anterior region of the user's eye.    -   60. The system of any of Examples 49 to 59, wherein the        reflective surface is configured to collimate light from the        cornea of the user's eye.    -   61. The system of any of Examples 49 to 60, wherein the        reflective surface is formed on a curved optical element and        comprises an infrared reflective coating.    -   62. The system of Example 61, wherein the curved optical element        has negligible power for light transmitted therethrough.    -   63. The system of Example 61 or 62, wherein the curved optical        element has first and second curved surfaces on opposite sides        of the curved optical element, said first and second curved        surfaces having the same curvature.    -   64. The system of any of Examples 49 to 63, further comprising a        retarder disposed with respect to the reflective surface and the        coupling optical element so as to rotate the polarization of        light passing through the at least one waveguide and reflected        from the reflective surface back to the at least one waveguide        and the coupling optical element.    -   65. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization selective        turning element.    -   66. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization grating.    -   67. The system of any of the Examples above, wherein the at        least one coupling element is configured to turn light guided        within the at least one waveguide out of the waveguide to the        eye as collimated light directed to the eye of the user.    -   68. The system of any of the Examples above, wherein the at        least one coupling element is configured to turn collimated        light from the reflective surface into the at least one        waveguide.    -   69. The system of any of the Examples above, wherein the at        least one out-coupling element comprises an off-axis reflector.    -   70. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization        selective turning element.    -   71. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization grating.    -   72. The system of any of the Examples above, wherein the at        least one out-coupling element comprises liquid crystal.    -   73. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a liquid crystal        polarization grating.    -   74. The system of any of the Examples above, further comprising        a circular polarizer.    -   75. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization selective turning        element.    -   76. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization grating.    -   77. The system of any of the Examples above, wherein the at        least one in-coupling element comprises a diffractive optical        element.    -   78. The system of any of the Examples above, wherein the at        least one in-coupling element comprises a diffraction grating.    -   79. The system of any of the Examples above, wherein the        in-coupling element comprises an off-axis reflector.    -   80. The system of any of Examples 49 to 79, wherein the        reflective surface comprises a liquid crystal reflector.    -   81. The system of any of Examples 49 to 80, wherein the        reflective surface comprises a cholesteric liquid crystal        reflective lens.    -   82. The system of any of the Examples above, wherein the same        waveguide (a) guides light coupled from the user's eye into said        at least one waveguide to be received by said camera so as to        capture an image of at least a portion of the eye of the user,        and (b) guides light coupled from said image projector such that        light from said projector can be directed to said user's eye        such that said image from said image projector is in the vision        field of said the user.    -   83. The system of any of the Examples above, wherein the same        coupling element (a) couples light from said user's eye into        said at least one waveguide to be received by said camera        and (b) couples light from said image projector out from said at        least one waveguide to said user's eye.    -   84. The system of any of Examples 49 to 83, further comprising        electronics configured to cause the camera to capture a first        image when light reflected from the reflective surface is        blocked.    -   85. The system of Example 84, wherein said electronics is        configured to cause the camera to capture a second image when        light reflected from the reflective surface is not blocked.    -   86. The system of Example 85, wherein said electronics is        configured to use the first image to modify the second image.    -   87. The system of Examples 85 or 86, wherein said electronics is        configured to subtract from the second image based on the first        image.    -   88. The system of any of the Examples above, wherein said system        is configured to perform eye tracking based images of said eye.    -   89. The system of Example 88, wherein performing eye tracking        based on said images of said eye comprises storing an image of        the retina of said eye.    -   90. The system of any of any of the Examples above, wherein said        system is configured to:        -   obtain an image of a portion of said retina of said eye            using said camera;        -   compare one or more stored images of said retina with the            image of said portion of said retina; and        -   determine a gaze of the user based on the comparison of the            one or more stored images and the image of the portion of            the retina obtained from the camera.    -   91. The system of Example 90, wherein determining a gaze of the        user comprises determining to which portion of the retina        corresponds to the image of said portion of the retina.    -   92. The system of any of Examples 90 to 91, wherein determining        a gaze of the user comprises determining an orientation of the        eye.    -   93. The system of any of the Examples above, wherein said system        is configured to obtain biometric data based on one or more        images of the user's eye obtained with said camera.    -   94. The system of any of the Examples above, wherein said system        is configured to identify the user via biometric sensing based        on one or more images of said eye obtained with said camera.    -   95. The system of any of the above Examples, wherein said system        is configured to provide illumination of a first polarization        and to preferentially capture images with said camera using        light of a second polarization different than said first        polarization.    -   96. The system of any of the above Examples, wherein said system        is configured to illuminate said user's eye with light of a        first polarization and to preferentially capture images of said        user's eye with said camera using light of a second polarization        different than said first polarization.    -   97. The system of Examples 95 or 96, wherein said first and        second polarizations are orthogonal.    -   98. The system of any of the above Examples, further comprising        a light source disposed so as to provide illumination so as to        capture images with said camera.    -   99. The system of any of the above Examples, further comprising        a light source disposed so as to illuminate of the user's eye.    -   100. The system of Examples 98 or 99, wherein said light source        comprises one or more infrared light sources.    -   101. The system of any of Examples 98 to 100, wherein said light        source comprises one or more infrared light emitting diodes        (LEDs).    -   102. The system of any of Examples 98 to 101, wherein said light        source is pulsed.    -   103. The system of any of Examples 98 to 102 further comprising        an off-axis reflector disposed to receive light from said light        source and illuminate said user's eye with said light.    -   104. The system of any of Examples 98 to 103, wherein said light        source is configured to input light into a waveguide to provide        said illumination.    -   105. The system of any of Examples 98 to 104, wherein said light        source is configured to input light into a waveguide disposed        with respect to said eye to provide illumination to said eye.    -   106. The system of Examples 104 or 105, further comprising an        illumination in-coupling optical element configured to couple        light from said light source into said waveguide.    -   107. The system of any of Examples 98 to 103, wherein said light        source is configured to input light into said at least one        waveguide to provide illumination.    -   108. The system of Example 107, further comprising an        illumination in-coupling optical element configured to couple        light from said light source into said at least one waveguide to        provide illumination.    -   109. The system of any of Examples 98 to 103, wherein said light        source is configured to input light into the same waveguide as        used to project image content to the user's eye.    -   110. The system of any of Examples 98 to 104, wherein said light        source is configured, to provide illumination to the user's eye,        to input light into the same waveguide as used to guide light to        the camera.    -   111. The system of any of Examples 98 to 105, wherein said light        source is configured to input light into the same waveguide as        used to guide light from the user's eye to the camera.    -   112. The system of any of Examples 109 to 111, further        comprising an illumination in-coupling optical element        configured to couple light from said light source into said        waveguide.    -   113. The system of any of Examples 106, 108, or 112, wherein        said illumination in-coupling optical element is polarization        selective, in-coupling light of a first polarization.    -   114. The system of Example 98 to 113, wherein said light source        is a polarized light source configured to output polarized light        having a first polarization.    -   115. The system of any of Examples 98 to 114, wherein said light        source is configured to direct polarized light having a first        polarization onto said eye.    -   116. The system of Example 98 to 115, further comprising an        illumination polarizer having a first polarization disposed in        the optical path between said light source and said eye to        polarize light directed to said eye.    -   117. The system of Example 116, wherein the illumination        polarizer is disposed in the optical path between said light        source and said waveguide configured to provide illumination.    -   118. The system of any of Examples 98 to 117, further comprising        an image acquisition polarizer in an optical path between said        eye and said camera.    -   119. The system of Example 118, wherein said image acquisition        polarizer is proximal said camera.    -   120. The system of Examples 118 or 119, wherein said image        acquisition polarizer is disposed in an optical path between (a)        said at least one waveguide configured guide light to said        camera and (b) said camera.    -   121. The system of any of Examples 118 to 120, wherein said        image acquisition polarizer reduces the amount of light said        first polarization that reaches said camera.    -   122. The system of Examples 118 to 121, wherein said image        acquisition polarizer comprises a polarizer configured to        selectively coupling light of a second polarization different        than said first polarization to said camera.    -   123. The system of any of the Examples above, further comprising        at least one light consolidating element disposed in an optical        path between said at least one coupling element and said at        least one out-coupling optical element to reduce lateral spatial        extent of light from said at least one coupling element prior to        reaching said at least one out-coupling optical element.    -   124. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a diffractive        optical element.    -   125. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a hologram or        diffraction grating.    -   126. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        infrared light having a refractive index sufficient to guide        infrared light in said waveguide by total internal reflection.    -   127. The system of any of the Examples above, wherein said at        least one coupling optical element comprises an exit pupil        expander.    -   128. The system of any of the Examples above, wherein the system        includes optical power to increase collimation of light        reflected from the eye that is coupled into the waveguide to be        guided to the camera.    -   129. The system of any of the Examples above, wherein the system        includes optical power to increase collimation of light        reflected from an anterior portion of the eye that is coupled        into the waveguide to be guided to the camera.    -   130. The system of any of the Examples above, wherein the system        includes optical power to increase collimation of light        reflected from the cornea of the eye that is coupled into the        waveguide to be guided to the camera.    -   131. The system of any of Examples 128 to 130, wherein the        optical power comprises positive optical power.    -   132. The system of any of Examples 128 to 131, wherein the        optical power is provided by a lens.    -   133. The system of any of Examples 88 to 132, wherein the one or        more stored images of the retina of the eye comprise a composite        image of the retina of the eye generated using a plurality of        images of different portions of the retina of the eye.    -   134. The system of any of Examples 88 to 133, wherein the        composite image of the retina comprises a plurality of images of        the retina stitched together.    -   135. The system of any of Examples 88 to 134, wherein the        plurality of images of the retina stitched together comprises        images obtained when a fixation target was displayed in the        vision field of the user at various locations, respectively.    -   136. The system of any of Examples 88 to 135, wherein the one or        more stored images of the retina comprises images obtained when        a fixation target was displayed in the vision field of the user        at various locations, respectively.    -   137. The system of any of Examples 88 to 136, wherein the system        is further configured to use the obtained image of the portion        of the retina of the eye to update the composite image.    -   138. The system of any of Examples 88 to 137, wherein using the        obtained image of the portion of the retina to update the        composite image of the retina comprises stitching the obtained        image into a section of the composite image corresponding to the        portion of the retina shown in the obtained image.    -   139. The system of any of Examples 88 to 138, wherein the system        is further configured to apply a digital filter to the obtained        image of the portion of the retina of the eye to obtain a        filtered image of the portion of the retina.    -   140. The system of Examples 139, wherein the system is further        configured to compare one or more stored images of the retina        with the filtered image of the portion of the retina.    -   141. The system of any of Examples 139 to 140, wherein the        digital filter comprises a Frangi Filter.    -   142. The system of any of Examples 88 to 139, wherein the system        is configured to apply edge enhance the obtained image of the        portion of the retina.    -   143. The system of any of the Examples above, wherein said        system is configured to perform user identification verification        using images of the retina.    -   144. The system of any of the Examples above, wherein said        system is configured to:        -   obtain an image of a portion of said retina of said eye            using said camera;        -   compare one or more stored images of said retina with the            image of said portion of said retina.    -   145. The system of Example 144, wherein the one or more stored        images of the retina of the eye comprise a composite image of        the retina of the eye generated using a plurality of images of        different portions of the retina of the eye.    -   146. The system of any of Examples 144 to 145, wherein the        composite image of the retina comprises a plurality of images of        the retina stitched together.    -   147. The system of any of Examples 144 to 146, wherein the        plurality of images of the retina stitched together comprises        images obtained when a fixation target was displayed in the        vision field of the user at various locations, respectively.    -   148. The system of any of Examples 144 to 146, wherein the one        or more stored images of the retina comprises images obtained        when a fixation target was displayed in the vision field of the        user at various locations, respectively.    -   149. The system of any of Examples 144 to 148, wherein the        system is further configured to use the obtained image of the        portion of the retina of the eye to update the composite image.    -   150. The system of any of Examples 144 to 149, wherein using the        obtained image of the portion of the retina to update the        composite image of the retina comprises stitching the obtained        image into a section of the composite image corresponding to the        portion of the retina shown in the obtained image.    -   151. The system of any of Examples 144 to 150, wherein the        system is further configured to apply a digital filter to the        obtained image of the portion of the retina of the eye to obtain        a filtered image of the portion of the retina.    -   152. The system of Examples 151, wherein the system is further        configured to compare one or more stored images of the retina        with the filtered image of the portion of the retina.    -   153. The system of any of Examples 144 to 152, wherein the        digital filter comprises a Frangi Filter.    -   154. The system of any of Examples 144 to 153, wherein the        system is configured to apply edge enhance the obtained image of        the portion of the retina.    -   155. The system of any of the Examples above, wherein said at        least one coupling optical element comprises a diffractive        optical element having a coupling area for coupling light into        said waveguide, said coupling area having an average thickness        in a range from 0.1 to 3 millimeters across, and wherein the        light is coupled into said waveguide via the coupling area of        the coupling element.    -   156. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.5        to 2 millimeters.    -   157. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 1 to        2 millimeters.    -   158. The system of any of the Examples above, wherein said        coupling area is slit shaped.    -   159. The system of any of the Examples above, wherein said        coupling area has a rectangular shape.    -   160. The system of any of the Examples above, wherein said        coupling area has an arcuate shape.    -   161. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 5 to 100.    -   162. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 10 to 100.    -   163. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 15 to 100.    -   164. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 20 and 100.    -   165. The system of any of the Examples above, wherein said        out-coupling optical element comprises a diffractive optical        element.    -   166. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 0.5 mm to 3.0 millimeters.    -   167. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters.    -   168. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        0.5 mm to 3.0 millimeters across in two orthogonal directions.    -   169. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        1.0 mm to 2.5 millimeters across in two orthogonal directions.    -   170. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio in a range from 1 to 2.    -   171. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio in a range from 1 to 1.75.    -   172. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.5.    -   173. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.3.    -   174. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.2.    -   175. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.1.    -   176. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said at least one camera.    -   177. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from an anterior portion of the eye of the user        wearing the head mounted display system is coupled into said        waveguide and guided therein such that images of said eye may be        captured by said camera such that said at least one camera can        capture images of said anterior portion of said eye.    -   178. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from a corneal surface of said eye of the user wearing        the head mounted display system is coupled into said waveguide        and guided therein such that images of said eye may be captured        by said camera such that said at least one camera can capture        images of said corneal surface of said eye.    -   179. The system of any of the Examples above, wherein the        coupling optical element has optical power.    -   180. The system of any of the Examples above, wherein the        optical power of the coupling optical element is configured to        increase collimation of light reflected from the eye that is        coupled into the waveguide to be guided to the camera.    -   181. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured to        increase collimation of light reflected from an anterior portion        of the eye that is coupled into the waveguide to be guided to        the camera.    -   182. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured to        increase collimation of light reflected from the cornea of the        eye that is coupled into the waveguide to be guided to the        camera.    -   183. The system of any of Examples above, wherein the optical        power comprises positive optical power.    -   184. The system of any of Examples above, wherein the optical        power corresponds to a focal length of in a range from 15 mm and        25 mm.    -   185. The system of any of Examples above, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said at        least one of said at least one waveguide out thereof such that        image content can be viewed by the user's eye.    -   186. The system of any of Examples above, wherein said at least        one image content out-coupling optical element and said at least        one coupling optical element are disposed laterally with respect        to each other.    -   187. The system of any of Example 186, wherein said at least one        image content out-coupling optical element is disposed more        nasally than said at least one out-coupling element.    -   188. The system of any of Example 186, wherein said at least one        image content out-coupling optical element is disposed more        temporally than said at least one out-coupling element.    -   189. The system of any of Examples above, wherein said at least        one coupling optical element comprises:        -   a first coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras; and        -   a second coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras,        -   wherein first coupling optical element and said second            coupling optical element are disposed laterally with respect            to each other.    -   190. The system of any of Example 189, wherein said first        coupling optical element comprising a diffractive optical        element having optical power.    -   191. The system of any of the Examples above, further comprising        a lens disposed with respect to said first coupling optical        element to provide optical power to light received by said first        coupling optical element.    -   192. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from the eye that is coupled into the waveguide to be        guided to the camera.    -   193. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from an anterior portion of the eye that is coupled        into the waveguide to be guided to the camera.    -   194. The system of any of the Examples above, wherein said        optical power is configured increase collimation of light        reflected from the cornea of the eye that is coupled into the        waveguide to be guided to the camera.    -   195. The system of any of the Examples above, wherein the        optical power comprises positive optical power.    -   196. The system of any of the Examples above, wherein the        optical power corresponds to a focal length about the distance        of the eye to first coupling optical element.    -   197. The system of any of any the Examples above, wherein the        optical power corresponds to a focal length in a range from 15        mm to 25 mm.    -   198. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from an anterior portion of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of said anterior portion of said eye        may be captured by said camera.    -   199. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from a corneal surface of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of the corneal surface said eye may be        captured by said camera.    -   200. The system of any of the Examples above, wherein said        second coupling optical element is configured such that light        reflected from the retina of the eye of the user wearing the        head mounted display system is coupled into said waveguide and        guided therein such that images of the retina of said eye may be        captured by said camera.    -   201. The system of any of the Examples above, wherein said        second coupling optical element does not include optical power.    -   202. The system of any of the Examples above, wherein said        second coupling optical element does not include a lens in an        optical path between the eye and said second coupling optical        element.    -   203. The system of any of the Examples above, wherein at least        one coupling optical element is configured such that light is        coupled into said waveguide and guided therein, said at least        one coupling optical element comprising a diffractive optical        element having a slit shaped coupling area for coupling light        into said waveguide, and wherein the camera is disposed in an        optical path with respect to said at least one out-coupling        optical element to receive at least a portion of the light that        is coupled into said waveguide via the coupling area of the        coupling element.    -   204. The system of any of the Examples above, wherein said        coupling area has an average thickness of in a range from 0.5 to        3 millimeters.    -   205. The system of any of the Examples above, wherein said        coupling area has an average thickness in a range from 0.5 to 2        millimeters.    -   206. The system of any of the Examples above, wherein said        coupling area has an average thickness in a range from 1 to 2        millimeters.    -   207. The system of any of the Examples above, wherein said        coupling area has a rectangular shape.    -   208. The system of any of the Examples above, wherein said        coupling area has an arcuate shape.    -   209. The system of any of the Examples above, wherein said        coupling area has a non-arcuate shape.    -   210. The system of any of the Examples above, wherein said        coupling area that has a length and a width, the length longer        than the width and said coupling area is straight along said the        length.    -   211. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 5 to 100.    -   212. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 10 to 100.    -   213. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 15 to 100.    -   214. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 20 to 100.    -   215. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a thickness from mm to 3.0        millimeters across.    -   216. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters across.    -   217. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension along one        direction of in a range from 0.5 mm to 3.0 millimeters across in        two orthogonal dimensions.    -   218. The system of any of the Examples above, wherein said        out-coupling optical element has an coupling area having a        dimension along one direction in a range from 1.0 mm to 2.5        millimeters across in two orthogonal dimensions.    -   219. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 2.    -   220. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.75.    -   221. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.5.    -   222. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.3.    -   223. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.2.    -   224. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.1.    -   225. The system of any of the Examples above, said at least one        out-coupling element has a coupling area for coupling light out        of said waveguide that is not a slit.    -   226. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.3 millimeters.    -   227. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 2 millimeters.    -   228. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 1.5 millimeters.    -   229. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 1 millimeters.    -   230. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 2 millimeters.    -   231. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 2 millimeters.    -   232. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 1.5 millimeters.    -   233. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 1 millimeters.    -   234. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 1.5 millimeters.    -   235. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 1 millimeters.    -   236. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.5 millimeters.    -   237. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.8 millimeters.    -   238. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.5 millimeters.    -   239. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.8 millimeters.    -   240. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.2 millimeters.    -   241. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.3 millimeters.    -   242. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.3 millimeters.    -   243. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 0.5 millimeters.    -   244. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 0.8 millimeters.    -   245. The system of any of the Examples above, wherein said        coupling area has a length of from 20 mm to 50 mm.    -   246. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 40 mm.    -   247. The system of any of the Examples above, wherein said        coupling area has a length of from 2 mm to 20 mm.    -   248. The system of any of the Examples above, wherein said        coupling area has a length of from 5 mm to 20 mm.    -   249. The system of any of the Examples above, wherein said        coupling area has a length of from 1 mm to 10 mm.    -   250. The system of any of the Examples above, wherein said        coupling area has a length of from 0.5 mm to 2 mm.    -   251. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 20 mm.    -   252. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 30 mm.    -   253. The system of any of the Examples above, wherein said        coupling area has a length of from 6 mm to 18 mm.    -   254. The system of any of the Examples above, wherein said        system is configured such that light coupled into said waveguide        by said first coupling optical element is acted on by a first        total optical power and light coupled into said waveguide by        said second coupling optical element is acted on by a second        total optical power and said first total optical power is larger        than said second total optical power.    -   255. The system of any of the Examples above, wherein said first        coupling optical element has a first optical power and said        second coupling optical element has a second optical power, and        said first optical power is larger than said second optical        power.    -   256. The system of any of the Examples above, wherein said first        coupling optical element has a first lens associated therewith        having has a first optical power and said second coupling        optical element has associated therewith a second lens having a        second optical power, and said first optical power is larger        than said second optical power.

Example Section II

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user and to image at least a portion of an        environment in front of the user wearing the head mounted        display system, said head-mounted display system comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project an image;        -   a camera; and        -   an eyepiece disposed on the frame, said eyepiece configured            to direct light into said user's eye to display augmented            reality image content to the user's vision field, at least a            portion of said eyepiece being transparent and disposed at a            location in front of the user's eye when the user wears said            head-mounted display such that said transparent portion            transmits light from the environment in front of the user to            the user's eye to provide a view of the environment in front            of the user, said eyepiece comprising:            -   (a) at least one waveguide;            -   (b) at least one in-coupling optical element configured                to in-couple light from said image projector into said                at least one waveguide so as to guide light from said                image projector therein;            -   (c) at least one coupling optical element configured to                couple light from said image projector guided within                said waveguide out of said waveguide and direct said                light to the user's eye; and            -   (d) at least one out-coupling element configured to                couple light within said waveguide out of said waveguide                and direct said light to said camera,        -   wherein the image projector is disposed in an optical path            with respect to said at least one in-coupling optical            element to couple light from said image projector into said            waveguide to be guided therein such that said light is            coupled out from said waveguide by said at least one            coupling element to said user's eye such that said image            from said projector is in the vision field of said the user,        -   wherein said coupling element is configured such that light            from the environment in front of the user wearing the head            mounted display is coupled into said waveguide and guided            therein,        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light from the environment            in front of the user that is coupled into said waveguide via            the coupling element and guided therein and that is coupled            out from said waveguide by said outcoupling coupling element            such that images of said environment may be captured by said            camera, and        -   wherein the same waveguide (a) guides light coupled from            said environment into said waveguide to be received by said            camera so as to capture an image of at least a portion of            the environment in front of the user, and (b) guides light            coupled from said projector such that light from said            projector can be directed to said user's eye so that said            image from said projector is in the vision field of said the            user.    -   2. The system of Example 1, wherein said image projector        comprises a light source, a modulator, and projection optics.    -   3. The system of Example 1 or 2, wherein the image projector        comprises scanning optical fiber.    -   4. The system of any of Examples 2 or 3, wherein the modulator        comprises a light modulator.    -   5. The system of Example 4, wherein the light modulator        comprises a spatial light modulator.    -   6. The system of any of the Examples above, wherein said camera        comprises a detector array and imaging optics.    -   7. The system of Example 6, wherein said imaging optics is        configured to focus collimated light onto said detector array.    -   8. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        visible light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   9. The system of any of the Examples above, wherein said at        least one waveguide comprises a stack of waveguides.    -   10. The system of Example 9, wherein different waveguides of the        stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   11. The system of Example 9 or 10, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   12. The system of any of Examples 9, 10, or 11, wherein        different waveguides comprise first, second, and third        waveguides, said system is configured such that the first is for        red color light, the second for is green color light, and the        third is for blue color light.    -   13. The system of any of the Examples above, wherein the        in-coupling optical element comprises a diffractive optical        element or reflector.    -   14. The system of any of the Examples above, wherein the        coupling optical element comprises a diffractive optical        element.    -   15. The system of any of the Examples above, wherein the        out-coupling optical element comprises a diffractive optical        element.    -   16. The system of any of the Examples above, wherein the        coupling element is configured to increase a dimension of the        eyebox along at least one axis.    -   17. The system of Example 16, further comprising an orthogonal        pupil expander comprising at least one light redirecting element        in or on said at least one waveguide that is configured to        increase a dimension of an eyebox along an axis that is        orthogonal to the at least one axis.    -   18. The system of Example 17, wherein said at least one light        redirecting element comprises a diffractive optical element.    -   19. The system of any of the Examples above, wherein the same        coupling element (a) couples light from said environment into        said at least one waveguide to be received by said camera        and (b) couples light from said image projector out from said at        least one waveguide to said user's eye.    -   20. The system of any of the above Examples, further comprising        a reflective surface having optical power disposed to receive        light reflected from the user's eye that passes through said        eyepiece and to direct said light back to said eyepiece.    -   21. The system of Example 20, wherein said at least one coupling        element is configured such that light from the user's eye that        passes through the eyepiece and is reflected from the reflective        surface back to the eyepiece is coupled into said waveguide and        guided therein.    -   22. The system of any of Examples 20 to 21, wherein the camera        is disposed in an optical path with respect to said at least one        out-coupling optical element to receive at least a portion of        the light from the user's eye that is reflected from the        reflective surface and coupled into said waveguide via the        coupling element and guided therein and that is coupled out from        said waveguide by said outcoupling coupling element.    -   23. The system of any of Examples 20 to 22, wherein the        reflective surface reflects infrared light but transmits visible        light.    -   24. The system of any of Examples 20 to 23, wherein the        reflective surface is curved.

The system of any of Examples 20 to 24, wherein the reflective surfaceis disposed on a curved optical element.

-   -   26. The system of any of Examples 20 to 25, wherein the        reflective surface is disposed on a concave mirror.    -   27. The system of any of Examples 20 to 26, wherein the        reflective surface has positive optical power in reflection and        negligible optical power in transmission.    -   28. The system any of Examples 20 to 27, wherein the reflective        surface is configured to collimated light from the user's eye.    -   29. The system of any of Examples 20 to 28, wherein the        reflective surface is configured to collimate light from the        retina of the user's eye.    -   30. The system of any of Examples 20 to 29, wherein the        reflective surface is configured to collimate light from an        anterior region of the user's eye.    -   31. The system of any of Examples 20 to 30, wherein the        reflective surface is configured to collimate light from the        cornea of the user's eye.    -   32. The system of any of Examples 20 to 31, wherein the        reflective surface is formed on a curved optical element having        an infrared reflective coating on said reflective surface.    -   33. The system of Example 33, wherein the curved optical element        has negligible power for light transmitted therethrough.    -   34. The system of Example 32 or 33, wherein the curved optical        element has first and second curved surface on opposite sides of        the curved optical element, said first and second curved        surfaces having the same curvature.    -   35. The system of any of the Examples above, further comprising        a retarder disposed with respect to the reflective surface and        the coupling optical element so as to rotate the polarization of        light passing through the eye piece and reflected from the        reflective surface back to the eye piece and the coupling        optical element.    -   36. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization selective        turning element.    -   37. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization grating.    -   38. The system of any of the Examples above, wherein the at        least one coupling element is configured to turn light guided        within the at least one waveguide out of the waveguide to the        eye as collimated light directed to the eye of the user.    -   39. The system of any of the Examples above, wherein the at        least one coupling element is configured to turn collimated        light from the reflective surface into the at least one        waveguide.    -   40. The system of any of the Examples above, wherein the at        least one out-coupling element comprises an off-axis reflector.    -   41. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization        selective turning element.    -   42. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization grating.    -   43. The system of any of the Examples above, further comprising        a circular polarizer.    -   44. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization selective turning        element.    -   45. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization grating.    -   46. The system of any of the Examples above, wherein the        in-coupling element comprises an off-axis reflector.    -   47. The system of any of Examples 20 to 34, wherein the        reflective surface comprises a liquid crystal reflector.    -   48. The system of any of Examples 20 to 34 or 47, wherein the        reflective surface comprises a cholesteric liquid crystal        reflective lens.    -   49. The system of any of the Examples above, wherein the same        waveguide (a) guides light coupled from the user's eye into said        at least one waveguide to be received by said camera so as to        capture an image of at least a portion of the eye of the user,        and (b) guides light coupled from said image projector such that        light from said projector can be directed to said user's eye        such that said image from said image projector is in the vision        field of said the user.    -   50. The system of any of the Examples above, wherein the same        coupling element (a) couples light from said user's eye into        said at least one waveguide to be received by said camera        and (b) couples light from said image projector out from said at        least one waveguide to said user's eye.    -   51. The system of any of the Examples above, further comprising        electronics configured to cause the camera to capture a first        image when light reflected from the reflective surface is        blocked.    -   52. The system of Example 51, wherein said electronics is        configured to cause the camera to capture a second image when        light reflected from the reflective surface is not blocked.    -   53. The system of Example 52, wherein said electronics is        configured to use the first image to modify the second image.    -   54. The system of Example 53, wherein said electronics is        configured to subtract from the second image based on the first        image.    -   55. The system of any of the Examples above, wherein said system        is configured to perform eye tracking based on said image of        said eye.    -   56. The system of Example 55, wherein performing eye tracking        based on said image of said eye comprises storing an image of        the retina of said eye.    -   57. The system of any of any of the Examples above, wherein said        system is configured to:        -   store an image of the retina of said eye;        -   capture an image of a portion of said retina of said eye;        -   compare the stored image of said retina with the image of            said portion of said retina; and        -   determine a gaze of the user based on the comparison of the            stored image and image of the portion of the retina.    -   58. The system of Example 57, wherein determining a gaze of the        user comprises determining to which portion of the retina        corresponds to the image of said portion of the retina.    -   59. The system of any of Examples 57 to 58, wherein determining        a gaze of the user comprises determining an orientation of the        eye.

The system of any of the above Examples, further comprising a lightsource disposed so as to illuminate of the user's eye.

-   -   61. The system of Example 60, wherein said light source        comprises one or more infrared light sources configured to        direct infrared light to the user's eye.    -   62. The system of Examples 60 or 61, wherein said light source        comprises one or more infrared light emitting diodes (LEDs).    -   63. The system of any of Examples 60 to 62, wherein said light        source is pulsed.    -   64. The system of any of the Examples above, further comprising        an off-axis reflector disposed to receive light from said light        source and illuminate said eye with said light.    -   65. A head mounted imaging system configured to image at least a        portion of an environment in front of a user wearing the head        mounted imaging system, said head-mounted imaging system        comprising:        -   a frame configured to be supported on a head of the user;        -   a camera; and        -   an eyepiece disposed on the frame, at least a portion of            said eyepiece being transparent and disposed at a location            in front of the user's eye when the user wears said            head-mounted imaging system such that said transparent            portion transmits light from the environment in front of the            user to the user's eye to provide a view of the environment            in front of the user, said eyepiece comprising:            -   (a) at least one waveguide;            -   (b) at least one coupling optical element configured                such that light from the environment in front of the                user wearing the head mounted imaging system is coupled                into said waveguide and guided therein; and            -   (c) at least one out-coupling element configured to                couple light within said waveguide out of said waveguide                and direct said light to said camera,        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light from the environment            in front of the user that is coupled into said waveguide via            the coupling element and guided therein and that is coupled            out from said waveguide by said outcoupling coupling element            such that images of said environment may be captured by said            camera.    -   66. The system of Example 65, wherein said camera comprises a        detector array and imaging optics.    -   67. The system of Example 66, wherein said imaging optics is        configured to focus collimated light onto said detector array.    -   68. The system of any of Examples 65 to 67, wherein said at        least one waveguide comprises material that is transparent to        visible light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   69. The system of any of Examples 65 to 68, wherein said at        least one waveguide comprises a stack of waveguides.    -   70. The system of Example 69, wherein different waveguides of        the stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   71. The system of Example 69 or 70, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   72. The system of any of Examples 69 to 71, wherein different        waveguides comprise first, second, and third waveguides, said        system is configured such that the first is for red color light,        the second for is green color light, and the third is for blue        color light.    -   73. The system of any of Examples 65 to 72, wherein the coupling        optical element comprises a diffractive optical element.    -   74. The system of any of Examples 65 to 73, wherein the        out-coupling optical element comprises a diffractive optical        element.    -   75. The system of any of Examples 65 to 74, wherein the coupling        element is configured to increase a dimension of the eyebox        along at least one axis.    -   76. The system of Example 75, further comprising an orthogonal        pupil expander comprising at least one light redirecting element        in or on said at least one waveguide that is configured to        increase a dimension of an eyebox along an axis that is        orthogonal to the at least one axis.    -   77. The system of Example 76, wherein said at least one light        redirecting element comprises a diffractive optical element.    -   78. The system of any of Examples 65-77, wherein said at least        one coupling optical element comprises a diffractive optical        element having a coupling area for coupling light into said        waveguide, said coupling area having an average thickness in a        range from 0.1 to 3 millimeters across, and wherein the light is        coupled into said waveguide via the coupling area of the        coupling element.    -   79. The system of Example 78, wherein said average thickness of        said coupling area is in a range from 0.5 to 2 millimeters.    -   80. The system of any of Examples 78-79, wherein said average        thickness of said coupling area is in a range from 1 to 2        millimeters.    -   81. The system of any of Examples 78-80, wherein said coupling        area is slit shaped.    -   82. The system of any of Examples 78-81, wherein said coupling        area has a rectangular shape.    -   83. The system of any of Examples 78-81, wherein said coupling        area has an arcuate shape.    -   84. The system of any of Examples 78-83, wherein said coupling        area has an aspect ratio in a range from 5 to 100.    -   85. The system of any of Examples 78-83, wherein said coupling        area has an aspect ratio in a range from 10 to 100.    -   86. The system of any of Examples 78-83, wherein said coupling        area has an aspect ratio in a range from 15 to 100.    -   87. The system of any of Examples 78-83, wherein said coupling        area has an aspect ratio in a range from 20 and 100.    -   88. The system of any of Examples 78-87, wherein said        out-coupling optical element comprises a diffractive optical        element.    -   89. The system of any of Examples 78-88, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 0.5 mm to 3.0 millimeters.    -   90. The system of any of Examples 78-88, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters.    -   91. The system of any of Examples 78-88, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        0.5 mm to 3.0 millimeters across in two orthogonal directions.    -   92. The system of any of Examples 78-88, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        1.0 mm to 2.5 millimeters across in two orthogonal directions.    -   93. The system of any of Examples 78-92, wherein said coupling        area of said out-coupling optical element has an aspect ratio in        a range from 1 to 2.    -   94. The system of any of Examples 78-92, wherein said coupling        area of said out-coupling optical element has an aspect ratio in        a range from 1 to 1.75.    -   95. The system of any of Examples 78-92, wherein said coupling        area of said out-coupling optical element has an aspect ratio of        in a range from 1 to 1.5.    -   96. The system of any of Examples 78-92, wherein said coupling        area of said out-coupling optical element has an aspect ratio of        in a range from 1 to 1.3.    -   97. The system of any of Examples 78-92, wherein said coupling        area of said out-coupling optical element has an aspect ratio of        in a range from 1 to 1.2.    -   98. The system of any of Examples 78-92, wherein said coupling        area of said out-coupling optical element has an aspect ratio of        in a range from 1 to 1.1.    -   99. The system of any of Examples 78-98, wherein said at least        one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said at least one camera.    -   100. The system of any of Examples 78-99, wherein said at least        one coupling optical element is configured such that light        reflected from an anterior portion of the eye of the user        wearing the head mounted display system is coupled into said        waveguide and guided therein such that images of said eye may be        captured by said camera such that said at least one camera can        capture images of said anterior portion of said eye.    -   101. The system of any of Examples 78-100, wherein said at least        one coupling optical element is configured such that light        reflected from a corneal surface of said eye of the user wearing        the head mounted display system is coupled into said waveguide        and guided therein such that images of said eye may be captured        by said camera such that said at least one camera can capture        images of said corneal surface of said eye.    -   102. The system of any of Examples 78-101, wherein the coupling        optical element has optical power.    -   103. The system of Example 102, wherein the optical power of the        coupling optical element is configured to increase collimation        of light reflected from the eye that is coupled into the        waveguide to be guided to the camera.    -   104. The system of any of Examples 102-103, wherein the optical        power of said coupling optical element is configured to increase        collimation of light reflected from an anterior portion of the        eye that is coupled into the waveguide to be guided to the        camera.    -   105. The system of any of Examples 102-104, wherein the optical        power of said coupling optical element is configured to increase        collimation of light reflected from the cornea of the eye that        is coupled into the waveguide to be guided to the camera.    -   106. The system of any of Examples above, wherein the optical        power comprises positive optical power.    -   107. The system of any of Examples above, wherein the optical        power corresponds to a focal length of in a range from 15 mm and        25 mm.    -   108. The system of any of Examples above, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said at        least one of said at least one waveguide out thereof such that        image content can be viewed by the user's eye.    -   109. The system of any of Examples above, wherein said at least        one image content out-coupling optical element and said at least        one coupling optical element are disposed laterally with respect        to each other.    -   110. The system of any of Example 109, wherein said at least one        image content out-coupling optical element is disposed more        nasally than said at least one out-coupling element.    -   111. The system of any of Example 109, wherein said at least one        image content out-coupling optical element is disposed more        temporally than said at least one out-coupling element.    -   112. The system of any of Examples above, wherein said at least        one coupling optical element comprises:        -   a first coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras; and        -   a second coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras,            wherein first coupling optical element and said second            coupling optical element are disposed laterally with respect            to each other.    -   113. The system of any of Example 112, wherein said first        coupling optical element comprising a diffractive optical        element having optical power.    -   114. The system of any of Examples 112-113, further comprising a        lens disposed with respect to said first coupling optical        element to provide optical power to light received by said first        coupling optical element.    -   115. The system of any of Examples 113-114, wherein said optical        power is configured to increase collimation of light reflected        from the eye that is coupled into the waveguide to be guided to        the camera.    -   116. The system of any of Examples 113-115, wherein said optical        power is configured to increase collimation of light reflected        from an anterior portion of the eye that is coupled into the        waveguide to be guided to the camera.    -   117. The system of any of Examples 113-116, wherein said optical        power is configured increase collimation of light reflected from        the cornea of the eye that is coupled into the waveguide to be        guided to the camera.    -   118. The system of any of Examples 113-117, wherein the optical        power comprises positive optical power.    -   119. The system of any of Examples 113-119, wherein the optical        power corresponds to a focal length about the distance of the        eye to first coupling optical element.    -   120. The system of any of any the Examples above, wherein the        optical power corresponds to a focal length in a range from 15        mm to 25 mm.    -   121. The system of any of Examples 112-120, wherein said first        coupling optical element is configured such that light reflected        from an anterior portion of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of said anterior portion of said eye        may be captured by said camera.    -   122. The system of any of Examples 112-121, wherein said first        coupling optical element is configured such that light reflected        from a corneal surface of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of the corneal surface said eye may be        captured by said camera.    -   123. The system of any of Examples 112-122, wherein said second        coupling optical element is configured such that light reflected        from the retina of the eye of the user wearing the head mounted        display system is coupled into said waveguide and guided therein        such that images of the retina of said eye may be captured by        said camera.    -   124. The system of any of Examples 112-123, wherein said second        coupling optical element does not include optical power.    -   125. The system of any of Examples 112-124, wherein said second        coupling optical element does not include a lens in an optical        path between the eye and said second coupling optical element.    -   126. The system of any of Examples 112-125, wherein at least one        coupling optical element is configured such that light is        coupled into said waveguide and guided therein, said at least        one coupling optical element comprising a diffractive optical        element having a slit shaped coupling area for coupling light        into said waveguide, and wherein the camera is disposed in an        optical path with respect to said at least one out-coupling        optical element to receive at least a portion of the light that        is coupled into said waveguide via the coupling area of the        coupling element.    -   127. The system of any of Examples 78-126, wherein said coupling        area has an average thickness of in a range from 0.5 to 3        millimeters.    -   128. The system of any of Examples 78-126, wherein said coupling        area has an average thickness in a range from 0.5 to 2        millimeters.    -   129. The system of any of Examples 78-126, wherein said coupling        area has an average thickness in a range from 1 to 2        millimeters.    -   130. The system of any of Examples 78-129, wherein said coupling        area has a rectangular shape.    -   131. The system of any of Examples 78-129, wherein said coupling        area has an arcuate shape.    -   132. The system of any of Examples 78-130, wherein said coupling        area has a non-arcuate shape.    -   133. The system of any of Examples 78-132, wherein said coupling        area that has a length and a width, the length longer than the        width and said coupling area is straight along said the length.    -   134. The system of any of Examples 78-133, wherein said coupling        area has an aspect ratio in a range from 5 to 100.    -   135. The system of any of Examples 78-133, wherein said coupling        area has an aspect ratio in a range from 10 to 100.    -   136. The system of any of Examples 78-133, wherein said coupling        area has an aspect ratio in a range from 15 to 100.    -   137. The system of any of Examples 78-133, wherein said coupling        area has an aspect ratio in a range from 20 to 100.    -   138. The system of any of Examples 78-137, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a thickness from 0.5 mm to        3.0 millimeters across.    -   139. The system of any of Examples 78-137, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters across.    -   140. The system of any of Examples 78-139, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension along one        direction of in a range from 0.5 mm to 3.0 millimeters across in        two orthogonal dimensions.    -   141. The system of any of Examples 78-139, wherein said        out-coupling optical element has an coupling area having a        dimension along one direction in a range from 1.0 mm to 2.5        millimeters across in two orthogonal dimensions.    -   142. The system of any of Examples 78-141, wherein said at least        one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 2.    -   143. The system of any of Examples 78-142, wherein said at least        one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.75.    -   144. The system of any of Examples 78-142, wherein said at least        one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.5.    -   145. The system of any of Examples 78-142, wherein said at least        one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.3.    -   146. The system of any of Examples 78-142, wherein said at least        one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.2.    -   147. The system of any of Examples 78-142, wherein said at least        one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.1.    -   148. The system of any of Examples 78-147, said at least one        out-coupling element has a coupling area for coupling light out        of said waveguide that is not a slit.    -   149. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 0.3        millimeters.    -   150. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 2        millimeters.    -   151. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 1.5        millimeters.    -   152. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 1        millimeters.    -   153. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.2 to 2        millimeters.    -   154. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.3 to 2        millimeters.    -   155. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.2 to 1.5        millimeters.    -   156. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.2 to 1        millimeters.    -   157. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.3 to 1.5        millimeters.    -   158. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.3 to 1        millimeters.    -   159. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 0.5        millimeters.    -   160. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 0.8        millimeters.    -   161. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.2 to 0.5        millimeters.    -   162. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.2 to 0.8        millimeters.    -   163. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 0.2        millimeters.    -   164. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.1 to 0.3        millimeters.    -   165. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.2 to 0.3        millimeters.    -   166. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.3 to 0.5        millimeters.    -   167. The system of any of Examples 78-148, wherein said average        thickness of said coupling area is in a range from 0.3 to 0.8        millimeters.    -   168. The system of any of Examples 78-167, wherein said coupling        area has a length of from 20 mm to 50 mm.    -   169. The system of any of Examples 78-167, wherein said coupling        area has a length of from 10 mm to 40 mm.    -   170. The system of any of Examples 78-167, wherein said coupling        area has a length of from 2 mm to 20 mm.    -   171. The system of any of Examples 78-167, wherein said coupling        area has a length of from 5 mm to 20 mm.    -   172. The system of any of Examples 78-167, wherein said coupling        area has a length of from 1 mm to 10 mm.    -   173. The system of any of Examples 78-167, wherein said coupling        area has a length of from 0.5 mm to 2 mm.    -   174. The system of any of Examples 78-167, wherein said coupling        area has a length of from 10 mm to 20 mm.    -   175. The system of any of Examples 78-167, wherein said coupling        area has a length of from 10 mm to 30 mm.    -   176. The system of any of Examples 78-167, wherein said coupling        area has a length of from 6 mm to 18 mm.

Example Section III

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user and to image at least a portion of the        eye of the user wearing the head mounted display system, said        head-mounted display system comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project an image;        -   a camera;        -   an eyepiece disposed on the frame, said eyepiece configured            to direct light into said user's eye to display augmented            reality image content to the user's vision field, at least a            portion of said eyepiece being transparent and disposed at a            location in front of the user's eye when the user wears said            head-mounted display such that said transparent portion            transmits light from the environment in front of the user to            the user's eye to provide a view of the environment in front            of the user, said eyepiece comprising:            -   (a) at least one waveguide;            -   (b) at least one in-coupling optical element configured                to in-couple light from said image projector into said                at least one waveguide so as to guide light from said                image projector therein;            -   (c) at least one coupling optical element configured to                couple light from said image projector guided within                said waveguide out of said waveguide and direct said                light to the user's eye; and            -   (d) at least one out-coupling element configured to                couple said light guided within said waveguide out of                said waveguide and direct said light to said camera; and        -   a reflective surface having optical power disposed to            receive light reflected from the user's eye that passes            through said eyepiece and to direct said light back to said            eyepiece;        -   wherein the image projector is disposed in an optical path            with respect to said at least one in-coupling optical            element to in-couple light from said image projector into            said waveguide to be guided therein such that said light is            coupled out from said waveguide by said at least one            coupling element to said user's eye such that said image            from said projector is in the vision field of said the user,        -   wherein said at least one coupling element is configured            such that light from the user's eye that passes through the            eyepiece and is reflected from the reflective surface back            to the eyepiece is coupled into said waveguide and guided            therein, and        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light from the user's eye            that is reflected from the reflective surface and coupled            into said waveguide via the coupling element and guided            therein and that is coupled out from said waveguide by said            outcoupling coupling element.    -   2. The system of Example 1, further comprising a light source        disposed so as to illuminate of the user's eye.    -   3. The system of Example 2, wherein said light source comprises        one or more infrared light sources configured to direct infrared        light to the user's eye.    -   4. The system of Examples 2 or 3, wherein said light source        comprises one or more infrared light emitting diodes (LEDs).    -   5. The system of any of Examples 2 to 4, wherein said light        source is pulsed.    -   6. The system of any of the Examples above, further comprising        an off-axis reflector disposed to receive light from said light        source and illuminate said eye with said light.    -   7. The system of any of the Examples above, wherein the        reflective surface reflects infrared light but transmits visible        light.    -   8. The system of any of the Examples above, wherein the        reflective surface is curved.    -   9. The system of any of the Examples above, wherein the        reflective surface is disposed on a curved optical element.    -   10. The system of any of the Examples above, wherein the        reflective surface is disposed on a concave mirror.    -   11. The system of any of the Examples above, wherein the        reflective surface has positive optical power in reflection and        negligible optical power in transmission.    -   12. The system of any of the Examples above, wherein the        reflective surface is configured to collimated light from the        user's eye.    -   13. The system of any of the Examples above, wherein the        reflective surface is configured to collimate light from the        retina of the user's eye.    -   14. The system of any of the Examples above, wherein the        reflective surface is configured to collimate light from an        anterior region of the user's eye.    -   15. The system of any of the Examples above, wherein the        reflective surface is configured to collimate light from the        cornea of the user's eye.    -   16. The system of any of the Examples above, wherein the        reflective surface is formed on a curved optical element having        an infrared reflective coating on said reflective surface.    -   17. The system of Example 9 or 16, wherein the curved optical        element has negligible power for light transmitted therethrough.    -   18. The system of any of Examples 9 or 16 or 17, wherein the        curved optical element has first and second curved surface on        opposite sides of the curved optical element, said first and        second curved surfaces having the same curvature.    -   19. The system of any of the Examples above, further comprising        a retarder disposed with respect to the reflective surface and        the coupling optical element so as to rotate the polarization of        light passing through the eye piece and reflected from the        reflective surface back to the eye piece and the coupling        optical element.    -   20. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization selective        turning element.    -   21. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization grating.    -   22. The system of any of the Examples above, wherein the at        least one coupling element is configured to turn light guided        within the at least one waveguide out of the waveguide to the        eye as collimated light directed to the eye of the user.    -   23. The system of any of the Examples above, wherein the at        least one coupling element is configured to turn collimated        light from the reflective surface into the at least one        waveguide.    -   24. The system of any of the Examples above, wherein the at        least one out-coupling element comprises an off-axis reflector.    -   25. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization        selective turning element.    -   26. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization grating.    -   27. The system of any of the Examples above, further comprising        a circular polarizer.    -   28. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization selective turning        element.    -   29. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization grating.    -   30. The system of any of the Examples above, wherein the        in-coupling element comprises an off-axis reflector.    -   31. The system of any of the Examples above, wherein the        reflective surface comprises a liquid crystal reflector.    -   32. The system of any of the Examples above, wherein the        reflective surface comprises a cholesteric liquid crystal        reflective lens.    -   33. The system of any of the Examples above, wherein said image        projector comprises a light source, a modulator, and projection        optics.    -   34. The system of any of the Examples above, wherein the image        projector comprises scanning optical fiber.    -   35. The system of any of the Examples above, wherein the        modulator comprises a light modulator.    -   36. The system of Example 34, wherein the light modulator        comprises a spatial light modulator.    -   37. The system of any of the Examples above, wherein said camera        comprises a detector array and imaging optics.    -   38. The system of Example 36, wherein said imaging optics is        configured to focus collimated light onto a detector array.    -   39. The system of any of the Examples above, wherein said at        least one waveguide comprises material transparent to visible        light having a refractive index sufficient to guide light in        said waveguide by total internal reflection.    -   40. The system of any of the Examples above, wherein said at        least one waveguide comprises a stack of waveguides.    -   41. The system of Example 40, wherein different waveguides of        the stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   42. The system of Example 40 or 41, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   43. The system of any of Examples 40, 41, or 42, wherein        different waveguides comprise first, second, and third        waveguides, said system is configured such that said first is        for red color light, the second for is green color light, and        the third is for blue color light.    -   44. The system of any of the Examples above, wherein the        in-coupling optical element comprises a diffractive optical        element or reflector.    -   45. The system of any of the Examples above, wherein the        coupling optical element comprises a diffractive optical        element.    -   46. The system of any of the Examples above, wherein the        out-coupling optical element comprises a diffractive optical        element.    -   47. The system of any of the Examples above, wherein the        coupling element is configured to increase dimensions of the        eyebox along at least one axis.    -   48. The system of Example 47, further comprising an orthogonal        pupil expander comprising at least one light redirecting element        in or on said at least one waveguide that is configured to        increase a dimension of an eyebox along an axis that is        orthogonal to the at least one axis.    -   49. The system of Example 48, wherein said at least one light        redirecting element comprises a diffractive optical element.    -   50. The system of any of the Examples above, wherein the same        waveguide (a) guides light coupled from the user's eye into said        at least one waveguide to be received by said camera so as to        capture an image of at least a portion of the eye of the user,        and (b) guides light coupled from said image projector such that        light from said projector can be directed to said user's eye        such that said image from said image projector is in the vision        field of said the user    -   51. The system of any of the Examples above, wherein the same        coupling element (a) couples light from said user's eye into        said at least one waveguide to be received by said camera        and (b) couples light from said image projector out from said at        least one waveguide to said user's eye.    -   52. The system of any of the Examples above, further comprising        electronics configured to cause the camera to capture a first        image when light reflected from the reflective surface is        blocked.    -   53. The system of Example 52, wherein said electronics is        configured to cause the camera to capture a second image when        light reflected from the reflective surface is not blocked.    -   54. The system of Example 53, wherein said electronics is        configured to use the first image to modify the second image.    -   55. The system of Example 54, wherein said electronics is        configured to subtract from the second image based on the first        image.    -   56. The system of any of the Examples above, wherein said system        is configured to perform eye tracking based on said image of        said eye.    -   57. The system of Example 56, wherein performing eye tracking        based on said image of said eye comprises storing an image of        the retina of said eye.    -   58. The system of any of any of the Examples above, wherein said        system is configured to:        -   store an image of the retina of said eye;        -   capture an image of a portion of said retina of said eye;        -   compare the stored image of said retina with the image of            said portion of said retina; and        -   determine a gaze of the user based on the comparison of the            stored image and image of the portion of the retina.    -   59. The system of Example 58, wherein determining a gaze of the        user comprises determining to which portion of the retina        corresponds to the image of said portion of the retina.    -   60. The system of any of Examples 58 to 59, wherein determining        a gaze of the user comprises determining an orientation of the        eye.    -   61. The system of any of the above Examples, wherein said        coupling element is configured such that light from the        environment in front of the user wearing the head mounted        display is coupled into said waveguide and guided therein.    -   62. The system of any of the above Examples, wherein the camera        is disposed in an optical path with respect to said at least one        out-coupling optical element to receive at least a portion of        the light from the environment in front of the user that is        coupled into said waveguide via the coupling element and guided        therein and that is coupled out from said waveguide by said        outcoupling coupling element such that images of said        environment may be captured by said camera.    -   63. The system of any of the above Examples, wherein the same        waveguide (a) guides light coupled from said environment into        said waveguide to be received by said camera so as to capture an        image of at least a portion of the environment in front of the        user, and (b) guides light coupled from said projector such that        light from said projector can be directed to said user's eye so        that said image from said projector is in the vision field of        said the user.    -   64. The system of any of the above Examples, wherein the same        coupling element (a) couples light from said environment into        said at least one waveguide to be received by said camera        and (b) couples light from said image projector out from said at        least one waveguide to said user's eye.    -   65. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user and to image at least a portion of the        eye of the user wearing the head mounted display system, said        head-mounted display system comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project an image;        -   a camera;        -   an eyepiece disposed on the frame, said eyepiece configured            to direct light into said user's eye to display augmented            reality image content to the user's vision field, at least a            portion of said eyepiece being transparent and disposed at a            location in front of the user's eye when the user wears said            head-mounted display such that said transparent portion            transmits light from an environment in front of the user to            the user's eye to provide a view of the environment in front            of the user, said eyepiece comprising:            -   (a) at least one waveguide;            -   (b) at least one in-coupling optical element configured                to in-couple light from said image projector into said                at least one waveguide so as to guide light from said                image projector therein;            -   (c) at least one coupling optical element configured to                couple light from said image projector guided within                said waveguide out of said waveguide and direct said                light to the user's eye; and            -   (d) at least one out-coupling element configured to                couple said light guided within said waveguide out of                said waveguide and direct said light to said camera; and        -   a positive lens having positive optical power disposed in an            optical path between the user's eye and said eyepiece such            that light reflected from the user's eye is transmitted            through said lens to said eyepiece; and        -   a negative lens having negative optical power disposed on            the other side of the eyepiece as the positive lens to            offset the power of said positive lens for light from the            environment in front of the user,        -   wherein the image projector is disposed in an optical path            with respect to said at least one in-coupling optical            element to couple light from said image projector into said            waveguide to be guided therein such that said light is            coupled out from said waveguide by said at least one            coupling element to said user's eye such that said image            from said image projector is in the vision field of said the            user,        -   wherein said at least one coupling element is configured            such that light from the user's eye that passes through the            lens to the eyepiece is coupled into said waveguide and            guided therein, and        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light from the user's eye            that is reflected from the reflective surface and coupled            into said waveguide via the coupling element and guided            therein and that is coupled out from said waveguide by said            out-coupling coupling element.    -   66. The system of Example 65, wherein said positive lens        comprises a Fresnel lens.    -   67. The system of Example 65 or 66, wherein said positive lens        is configured to collimate light from an anterior region of said        user's eye.    -   68. The system of any of Examples 65, 66, or 67 above, wherein        said positive lens is configured to collimate light from the        cornea of said user's eye.    -   69. The system of any of Examples 65 to 68, wherein said system        is configured to perform eye tracking based on said image of        said eye.    -   70. The system of any of Examples 65 to 69, further comprising a        light source disposed so as to illuminate of the user's eye.    -   71. The system of Example 70, wherein said light source        comprises one or more infrared light sources configured to        direct infrared light to the user's eye.    -   72. The system of Examples 70 or 71, wherein said light source        comprises one or more infrared light emitting diodes (LEDs).    -   73. The system of any of the Examples above, wherein said system        is configured to identify the user via biometric sensing based        on said image of said eye.

Example Section IV

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   at least one camera;        -   at least one waveguide;        -   at least one coupling optical element configured such that            light is coupled into said waveguide and guided therein,            said at least one coupling optical element comprising a            diffractive optical element having optical power; and        -   at least one out-coupling element configured to couple light            guided within said waveguide out of said waveguide and            direct said light to said camera,        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light that is coupled into            said waveguide via the coupling optical element and guided            therein and that is coupled out from said waveguide by said            out-coupling coupling element such that images may be            captured by said camera.    -   2. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said at least one camera.    -   3. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from an anterior portion of the eye of the user        wearing the head mounted display system is coupled into said        waveguide and guided therein such that images of said eye may be        captured by said camera such that said at least one camera can        capture images of said anterior portion of said eye.    -   4. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from a corneal surface of said eye of the user wearing        the head mounted display system is coupled into said waveguide        and guided therein such that images of said eye may be captured        by said camera such that said at least one camera can capture        images of said corneal surface of said eye.    -   5. The system of any of the Examples above, wherein the optical        power of said coupling optical element is configured to increase        collimation of light reflected from the eye that is coupled into        the waveguide to be guided to the camera.    -   6. The system of any of the Examples above, wherein the optical        power of said coupling optical element is configured to increase        collimation of light reflected from an anterior portion of the        eye that is coupled into the waveguide to be guided to the        camera.    -   7. The system of any of the Examples above, wherein the optical        power of said coupling optical element is configured increase        collimation of light reflected from the cornea of the eye that        is coupled into the waveguide to be guided to the camera.    -   8. The system of any of Examples 1 or 7, wherein the optical        power comprises positive optical power.    -   9. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the retina of the eye of the user wearing the        head mounted display system is coupled into said waveguide and        guided therein such that images of said retina may be captured        by said camera.    -   10. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   11. The system of Example 10, wherein said eyepiece is        configured to receive light from said image projector and to        direct said light into said user's eye to display augmented        reality image content to the user's vision field.    -   12. The system of any of Examples 10-11, wherein said eyepiece        comprises said at least one waveguide.    -   13. The system of any of Examples 10-12, wherein said image        projector is configured to direct light into an edge of said        eyepiece.    -   14. The system of Examples 12 or 13, wherein said image        projector is configured to direct light into an edge of said at        least one waveguide.    -   15. The system of any of the Examples above, further comprising        at least one in-coupling optical element configured to in-couple        light from said image projector into said at least one waveguide        so as to guide light from said image projector for providing        said image content to said user's eye.    -   16. The system of any of Examples 1 to 12, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said        waveguide out of said at least one waveguide such that image        content can be viewed by the user's eye.    -   17. The system of any of the Examples above, wherein said at        least one coupling optical element faces the eye of the user        wearing the head mounted imaging system to receive light from        said eye.    -   18. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        from the environment in front of the user wearing the head        mounted imaging system is coupled into said at least one        waveguide and guided therein such that images of said        environment may be captured by said camera.    -   19. The system of any of the Examples above, wherein said at        least one coupling optical element faces the environment in        front of the user wearing the head mounted imaging system to        receive light from said environment.    -   20. The system of Example 16, wherein said at least one coupling        optical element is configured such that light is coupled into a        first waveguide and guided therein to said camera and said at        least one image content out-coupling optical element is        configured to couple light from said image projector guided        within a second waveguide out of said second waveguide.    -   21. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        is coupled into a first waveguide and guided therein to said        camera and said image projector is configured to couple light        into a second waveguide to provide image content to said eye.    -   22. The system of any of the Examples above, wherein said image        projector comprises a light source, a modulator, and projection        optics.    -   23. The system of any of the Examples above, wherein the image        projector comprises scanning optical fiber.    -   24. The system of any of Examples 22, wherein the modulator        comprises a light modulator.    -   25. The system of Example 24, wherein the light modulator        comprises a spatial light modulator.    -   26. The system of any of the Examples above, wherein said camera        comprises a detector array and imaging optics.    -   27. The system of Example 26, wherein said imaging optics is        configured to focus collimated light onto said detector array.    -   28. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        visible light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   29. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        infrared light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   30. The system of any of the Examples above, wherein said at        least one waveguide comprises a stack of waveguides.    -   31. The system of Example 30, wherein different waveguides of        the stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   32. The system of Example 30 or 31, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   33. The system of any of Examples 30, 31, or 32, wherein        different waveguides comprise first, second, and third        waveguides, said system is configured such that the first is for        red color light, the second for is green color light, and the        third is for blue color light.    -   34. The system of any of the Examples 15 to 33, wherein the at        least one in-coupling optical element comprises a diffractive        optical element.    -   35. The system of any of the Examples 15 to 33, wherein the at        least one in-coupling optical element comprises a diffraction        grating.    -   36. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization selective turning        element.    -   37. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization grating.    -   38. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization selective        turning element.    -   39. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization grating.    -   40. The system of any of the Examples above, wherein the        coupling optical element comprises liquid crystal.    -   41. The system of any of the Examples above, wherein the        coupling optical element comprises a liquid crystal polarization        grating.    -   42. The system of any of the Examples above, wherein the        out-coupling optical element comprises a diffractive optical        element.    -   43. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization        selective turning element.    -   44. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization grating.    -   45. The system of any of the Examples above, wherein the at        least one out-coupling element comprises liquid crystal.    -   46. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a liquid crystal        polarization grating.    -   47. The system of any of the Examples above, wherein the at        least one out-coupling element comprises an off-axis reflector.    -   48. The system of any of the Examples above, wherein the same        waveguide (a) guides light coupled from the user's eye into said        at least one waveguide to be received by said camera so as to        capture an image of at least a portion of the eye of the user,        and (b) guides light coupled from said image projector such that        light from said projector can be directed to said user's eye        such that said image from said image projector is in the vision        field of said the user.    -   49. The system of any of the Examples above, wherein said system        is configured to perform eye tracking based images of said eye.    -   50. The system of Example 49, wherein performing eye tracking        based on said images of said eye comprises storing an image of        the retina of said eye.    -   51. The system of any of any of the Examples above, wherein said        system is configured to:        -   obtain an image of a portion of said retina of said eye            using said camera;        -   compare one or more stored images of said retina with the            image of said portion of said retina; and        -   determine a gaze of the user based on the comparison of the            one or more stored images and the image of the portion of            the retina obtained from the camera.    -   52. The system of Example 51, wherein determining a gaze of the        user comprises determining to which portion of the retina        corresponds to the image of said portion of the retina.    -   53. The system of any of Examples 51 to 52, wherein determining        a gaze of the user comprises determining an orientation of the        eye.    -   54. The system of any of the Examples above, wherein said system        is configured to obtain biometric data based on one or more        images of the user's eye obtained with said camera.    -   55. The system of any of the Examples above, wherein said system        is configured to identify the user via biometric sensing based        on one or more images of said eye obtained with said camera.    -   56. The system of any of the above Examples, wherein said system        is configured to provide illumination of a first polarization        and to preferentially capture images with said camera using        light of a second polarization different than said first        polarization.    -   57. The system of any of the above Examples, wherein said system        is configured to illuminate said user's eye with light of a        first polarization and to preferentially capture images of said        user's eye with said camera using light of a second polarization        different than said first polarization.    -   58. The system of Examples 60 or 61, wherein said first and        second polarizations are orthogonal.    -   59. The system of any of the above Examples, further comprising        a light source disposed so as to provide illumination so as to        capture images with said camera.    -   60. The system of any of the above Examples, further comprising        a light source disposed so as to illuminate of the user's eye.    -   61. The system of Examples 59 or 60, wherein said light source        comprises one or more infrared light sources.    -   62. The system of any of Examples 59 to 61, wherein said light        source comprises one or more infrared light emitting diodes        (LEDs).    -   63. The system of any of Examples 59 to 63, wherein said light        source is pulsed.    -   64. The system of any of Examples 59 to 63, wherein said light        source is configured to input light into a waveguide to provide        said illumination.    -   65. The system of any of Examples 59 to 64, wherein said light        source is configured to input light into a waveguide disposed        with respect to said eye to provide illumination to said eye.    -   66. The system of Examples 64 or 65, further comprising an        illumination in-coupling optical element configured to couple        light from said light source into said waveguide.    -   67. The system of any of Examples 60 to 66, wherein said light        source is configured to input light into said at least one        waveguide to provide illumination.    -   68. The system of any of Examples 59 to 68, wherein said light        source is configured to input light into the same waveguide as        used to project image content to the user's eye.    -   69. The system of any of Examples 59 to 69, wherein said light        source is configured, to provide illumination to the user's eye,        to input light into the same waveguide as used to guide light to        the camera.    -   70. The system of any of Examples 59 to 70, wherein said light        source is configured to input light into the same waveguide as        used to guide light from the user's eye to the camera.    -   71. The system of any of Examples 64 to 70, further comprising        an illumination in-coupling optical element configured to couple        light from said light source into said waveguide to provide        illumination.    -   72. The system of Example 71, wherein said illumination        in-coupling optical element is polarization selective,        in-coupling light of a first polarization.    -   73. The system of Example 59 to 77, wherein said light source is        a polarized light source configured to output polarized light        having a first polarization.    -   74. The system of any of Examples 59 to 78, wherein said light        source is configured to direct polarized light having a first        polarization onto said eye.    -   75. The system of Example 59 to 79, further comprising an        illumination polarizer having a first polarization disposed in        the optical path between said light source and said eye to        polarize light directed to said eye.    -   76. The system of Example 75, wherein the illumination polarizer        is disposed in the optical path between said light source and        said waveguide configured to provide illumination.    -   77. The system of any of Examples 59 to 76, further comprising        an image acquisition polarizer in an optical path between said        eye and said camera.    -   78. The system of Example 77, wherein said image acquisition        polarizer is proximal said camera.    -   79. The system of Examples 77 or 78, wherein said image        acquisition polarizer is disposed in an optical path between (a)        said at least one waveguide configured guide light to said        camera and (b) said camera.    -   80. The system of any of Examples 77 to 79, wherein said image        acquisition polarizer reduces the amount of light of said first        polarization that reaches said camera.    -   81. The system of Examples 77 to 80, wherein said image        acquisition polarizer comprises a polarizer configured to        selectively coupling light of a second polarization different        than said first polarization to said camera.    -   82. The system of any of the Examples above, further comprising        at least one light consolidating element disposed in an optical        path between said at least one coupling element and said at        least one out-coupling optical element to reduce lateral spatial        extent of light from said at least one coupling element prior to        reaching said at least one out-coupling optical element.    -   83. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a diffractive        optical element.    -   84. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a hologram or        diffraction grating.    -   85. The system of any of Examples 51, wherein the one or more        stored images of the retina of the eye comprise a composite        image of the retina of the eye generated using a plurality of        images of different portions of the retina of the eye.    -   86. The system of any of Examples 51 to 85, wherein the        composite image of the retina comprises a plurality of images of        the retina stitched together.    -   87. The system of any of Examples 51 to 86, wherein the        plurality of images of the retina stitched together comprises        images obtained when a fixation target was displayed in the        vision field of the user at various locations, respectively.    -   88. The system of any of Examples 51 to 87, wherein the one or        more stored images of the retina comprises images obtained when        a fixation target was displayed in the vision field of the user        at various locations, respectively.    -   89. The system of any of Examples 51 to 88, wherein the system        is further configured to use the obtained image of the portion        of the retina of the eye to update the composite image.    -   90. The system of any of Examples 51 to 89, wherein using the        obtained image of the portion of the retina to update the        composite image of the retina comprises stitching the obtained        image into a section of the composite image corresponding to the        portion of the retina shown in the obtained image.    -   91. The system of any of Examples 51 to 90, wherein the system        is further configured to apply a digital filter to the obtained        image of the portion of the retina of the eye to obtain a        filtered image of the portion of the retina.    -   92. The system of Examples 91, wherein the system is further        configured to compare one or more stored images of the retina        with the filtered image of the portion of the retina.    -   93. The system of any of Examples 91 to 92, wherein the digital        filter comprises a Frangi Filter.    -   94. The system of any of Examples 51 to 93, wherein the system        is configured to apply edge enhance the obtained image of the        portion of the retina.    -   95. The system of any of the Examples above, wherein said system        is configured to perform user identification verification using        images of the retina.    -   96. The system of any of the Examples above, wherein said system        is configured to:        -   obtain an image of a portion of said retina of said eye            using said camera;        -   compare one or more stored images of said retina with the            image of said portion of said retina.    -   97. The system of Example 96, wherein the one or more stored        images of the retina of the eye comprise a composite image of        the retina of the eye generated using a plurality of images of        different portions of the retina of the eye.    -   98. The system of any of Examples 96 to 97, wherein the        composite image of the retina comprises a plurality of images of        the retina stitched together.    -   99. The system of any of Examples 96 to 98, wherein the        plurality of images of the retina stitched together comprises        images obtained when a fixation target was displayed in the        vision field of the user at various locations, respectively.    -   100. The system of any of Examples 96 to 99, wherein the one or        more stored images of the retina comprises images obtained when        a fixation target was displayed in the vision field of the user        at various locations, respectively.    -   101. The system of any of Examples 96 to 100, wherein the system        is further configured to use the obtained image of the portion        of the retina of the eye to update the composite image.    -   102. The system of any of Examples 96 to 101, wherein using the        obtained image of the portion of the retina to update the        composite image of the retina comprises stitching the obtained        image into a section of the composite image corresponding to the        portion of the retina shown in the obtained image.    -   103. The system of any of Examples 96 to 102, wherein the system        is further configured to apply a digital filter to the obtained        image of the portion of the retina of the eye to obtain a        filtered image of the portion of the retina.    -   104. The system of Examples 103, wherein the system is further        configured to compare one or more stored images of the retina        with the filtered image of the portion of the retina.    -   105. The system of any of Examples 96 to 104, wherein the        digital filter comprises a Frangi Filter.    -   106. The system of any of Examples 96 to 105, wherein the system        is configured to apply edge enhancement the obtained image of        the portion of the retina.    -   107. The system of any of Examples above, wherein the optical        power corresponds to a focal length about the distance of the        eye to the coupling optical element.    -   108. The system of any of Examples above, wherein the optical        power corresponds to a focal length of between 15 mm and 25 mm.    -   109. A head mounted display system configured to project light        to an eye of a user to display augmented reality image content        in a vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   at least one waveguide,        -   an image projector for projecting images into the user's eye            to display image content in the vision field of the user,            said image projector configured to input light into at least            one of said at least one waveguide to be guided therein;        -   at least one image content out-coupling optical element            configured to couple light from said image projector guided            within said at least one of said at least one waveguide out            thereof such that image content can be viewed by the user's            eye.        -   a camera;        -   at least one coupling optical element configured such that            light is coupled into at least one of said at least one            waveguide and guided therein to said camera; and        -   at least one out-coupling element configured to couple light            guided within said at least one of said at least one            waveguide out thereof and direct said light to said camera,            said camera disposed in an optical path with respect to said            at least one out-coupling optical element to receive at            least a portion of the light that is coupled into said at            least one of said at least one waveguide via the coupling            optical element and guided therein and that is coupled out            from said at least one of said at least one waveguide by            said out-coupling coupling element such that images may be            captured by said camera,        -   wherein said at least one image content out-coupling optical            element and said at least one coupling optical element are            disposed laterally with respect to each other.    -   110. The system of any of Example 109, wherein said at least one        image content out-coupling optical element is disposed more        nasally than said at least one out-coupling element.    -   111. The system of any of Example 110, wherein said at least one        image content out-coupling optical element is disposed more        temporally than said at least one out-coupling element.    -   112. The system of any of the Examples above, further comprising        at least one light consolidating element disposed in an optical        path between said at least one coupling element and said at        least one out-coupling optical element to reduce lateral spatial        extent of light from said at least one coupling element prior to        reaching said at least one out-coupling optical element.    -   113. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a diffractive        optical element.    -   114. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a hologram or        diffraction grating.    -   115. The system of any of the Examples above, wherein said        coupling optical element comprises a diffractive optical element        having optical power.    -   116. The system of any of the Examples above, further comprising        a lens disposed with respect to said coupling optical element to        provide optical power to light received by said coupling optical        element.    -   117. The system of any of the Examples above, wherein the        optical power is configured to increase collimation of light        reflected from the eye that is coupled into the waveguide to be        guided to the camera.    -   118. The system of any of the Examples above, wherein the        optical power is configured to increase collimation of light        reflected from an anterior portion of the eye that is coupled        into the waveguide to be guided to the camera.    -   119. The system of any of the Examples above, wherein the        optical power is configured increase collimation of light        reflected from the cornea of the eye that is coupled into the        waveguide to be guided to the camera.    -   120. The system of any of Examples above, wherein the optical        power comprises positive optical power.    -   121. The system of any of Examples above, wherein the optical        power corresponds to a focal length about the distance of the        eye to the coupling optical element.    -   122. The system of any of Examples above, wherein the optical        power corresponds to a focal length of between 15 mm and 25 mm.    -   123. The system of any of the Examples above, wherein said        coupling optical element is configured such that light reflected        from the eye of the user wearing the head mounted display system        is coupled into said waveguide and guided therein such that        images of said eye may be captured by said camera, said system        configured to image an anterior portion of said eye.    -   124. The system of any of the Examples above, wherein said        coupling optical element is configured such that light reflected        from the eye of the user wearing the head mounted display system        is coupled into said waveguide and guided therein such that        images of said eye may be captured by said camera, said system        configured to image a corneal surface of said eye.    -   125. The system of any of the Examples above, wherein said        second coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said waveguide and guided therein        such that images of said eye may be captured by said camera,        said system configured to image the retina of said user's eye.    -   126. The system of any of the above Examples, wherein said        system is configured to provide illumination of a first        polarization and to preferentially capture images with said        camera using light of a second polarization different than said        first polarization.    -   127. The system of any of the above Examples, wherein said        system is configured to illuminate said user's eye with light of        a first polarization and to preferentially capture images of        said user's eye with said camera using light of a second        polarization different than said first polarization.    -   128. The system of Examples 126 or 127, wherein said first and        second polarizations are orthogonal.    -   129. The system of any of Examples 126 to 128, further        comprising an illumination in-coupling optical element        configured to couple light from a light source into said        waveguide to provide illumination.    -   130. The system of Example 129, wherein said illumination        in-coupling optical element is polarization selective,        in-coupling light of a first polarization.    -   131. The system of any of the Examples above, further comprising        a light source that is a polarized light source configured to        output polarized light having a first polarization.    -   132. The system of any of Example above, wherein said light        source is configured to direct polarized light having a first        polarization onto said eye.    -   133. The system of any of the Examples above, further comprising        an illumination polarizer having a first polarization disposed        in the optical path between said light source and said eye to        polarize light directed to said eye.    -   134. The system of Example 133, wherein the illumination        polarizer is disposed in the optical path between said light        source and said waveguide configured to provide illumination.    -   135. The system of any of the Example above, further comprising        an image acquisition polarizer in an optical path between said        eye and said camera.    -   136. The system of Example 135, wherein said image acquisition        polarizer is proximal said camera.    -   137. The system of Examples 135 or 136, wherein said image        acquisition polarizer is disposed in an optical path between (a)        said at least one waveguide configured guide light to said        camera and (b) said camera.    -   138. The system of any of Examples 135 to 137, wherein said        image acquisition polarizer reduces the amount of light of said        first polarization that reaches said camera.    -   139. The system of Examples 135 to 138, wherein said image        acquisition polarizer comprises a polarizer configured to        selectively coupling light of a second polarization different        than said first polarization to said camera.    -   140. A head mounted display system configured to project light        to an eye of a user to display augmented reality image content        in a vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   at least one camera;        -   at least one waveguide;        -   a first coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras;        -   a second coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras; and        -   at least one out-coupling element configured to couple light            coupled into said at least one waveguide by said first and            second coupling optical elements and guided within said at            least one waveguide out of said at least one waveguide and            direct said light to said at least one said camera,        -   wherein first coupling optical element and said second            coupling optical element are disposed laterally with respect            to each other.    -   141. The system of any of Example 140, wherein said first        coupling optical element comprising a diffractive optical        element having optical power.    -   142. The system of any of the Examples above, further comprising        a lens disposed with respect to said first coupling optical        element to provide optical power to light received by said first        coupling optical element.    -   143. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from the eye that is coupled into the waveguide to be        guided to the camera.    -   144. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from an anterior portion of the eye that is coupled        into the waveguide to be guided to the camera.    -   145. The system of any of the Examples above, wherein said        optical power is configured increase collimation of light        reflected from the cornea of the eye that is coupled into the        waveguide to be guided to the camera.    -   146. The system of any of the Examples above, wherein the        optical power comprises positive optical power.    -   147. The system of any of the Examples above, wherein the        optical power corresponds to a focal length about the distance        of the eye to first coupling optical element.    -   148. The system of any of any the Examples above, wherein the        optical power corresponds to a focal length of between 15 mm and        25 mm.    -   149. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from an anterior portion of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of said anterior portion of said eye        may be captured by said camera.    -   150. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from a corneal surface of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of the corneal surface said eye may be        captured by said camera.    -   151. The system of any of the Examples above, wherein said        second coupling optical element is configured such that light        reflected from the retina of the eye of the user wearing the        head mounted display system is coupled into said waveguide and        guided therein such that images of the retina of said eye may be        captured by said camera.    -   152. The system of any of the Examples above, wherein said        second coupling optical element does not include optical power.    -   153. The system of any of the Examples above, wherein said        second coupling optical element does not include a lens in an        optical path between the eye and said second coupling optical        element.    -   154. The system of any of the Examples above, wherein said first        and second coupling optical elements couple light into said        waveguide that is guided therein to a single camera.    -   155. The system of any of the Examples above, wherein said at        least one camera comprises first and second cameras, said first        coupling optical element configured to couples light into said        waveguide that is guided therein to said first camera and said        second coupling optical element configured to couple light into        said waveguide that is guided therein to the second camera.    -   156. The system of any of the Examples above, wherein said at        least one camera comprises a single cameras, said first and        second coupling optical element configured to couple light into        said waveguide that is guided therein to said single camera.    -   157. The system of any of the Examples above, wherein at least        one out-coupling element comprises a first out-coupling element        for out-coupling light that is input into said at least one        waveguide through said first coupling optical element and a        second out-coupling element for out-coupling light guided that        is input into said at least one waveguide through said second        coupling optical element.    -   158. The system of any of the above Examples, wherein said        system is configured to provide illumination of a first        polarization.    -   159. The system of Example 158, said system is configured such        that light received by said second coupling optical element is        preferentially used to captures images with light having a        second polarization different than said first polarization.    -   160. The system of any of the above Examples, wherein said        system is configured to illuminate said user's eye with light of        a first polarization.    -   161. The system of Example 160, wherein said system is        configured such that light received by said second coupling        optical element is preferentially used to captures images of        said eye with light having a second polarization different than        said first polarization.    -   162. The system of any of Examples 158 to 161, wherein said        system is configured such that light received by said first        coupling optical element enables capture of images of said eye        with light having either said first or second polarizations.    -   163. The system of any of Examples 158 to 162, wherein said        first and second polarizations are orthogonal.    -   164. The system of any of Examples 158 to 163, further        comprising an illumination in-coupling optical element        configured to couple light from a light source into said        waveguide to provide illumination.    -   165. The system of Example 164, wherein said illumination        in-coupling optical element is polarization selective,        in-coupling light of a first polarization.    -   166. The system of any of Examples 158 to 165, further        comprising a light source that is a polarized light source        configured to output polarized light having a first        polarization.    -   167. The system of any of Examples 158 to 166, wherein said        light source is configured to direct polarized light having a        first polarization onto said eye.    -   168. The system of any of Examples 158 to 167, further        comprising an illumination polarizer having a first polarization        disposed in the optical path between said light source and said        eye to polarize light directed to said eye.    -   169. The system of Example 168, wherein the illumination        polarizer is disposed in the optical path between said light        source and said waveguide configured to provide illumination.    -   170. The system of any of Examples 158 to 169, further        comprising an image acquisition polarizer in an optical path        between said eye and said camera.    -   171. The system of any of Examples 158 to 169, wherein said        image acquisition polarizer is disposed in an optical path        between said second coupling optical element and said at least        one camera that receives light from said second coupling optical        element.    -   172. The system of any of the Examples above, wherein at least        one out-coupling element comprises a first out-coupling element        for out-coupling light that is input into said at least one        waveguide through said first coupling optical element and a        second out-coupling element for out-coupling light guided that        is input into said at least one waveguide through said second        coupling optical element.    -   173. The system of any of Examples 158 to 169, wherein said        image acquisition polarizer is disposed in an optical path        between a second out-coupling coupling optical element and said        camera.    -   174. The system of Example 170, wherein said image acquisition        polarizer is proximal said camera.    -   175. The system of Examples 170 or 171, wherein said image        acquisition polarizer is disposed in an optical path between (a)        said at least one waveguide configured guide light to said        camera and (b) said camera.    -   176. The system of any of Examples 170 to 172, wherein said        image acquisition polarizer reduces the amount of light of said        first polarization that reaches said camera.    -   177. The system of Examples 170 to 173, wherein said image        acquisition polarizer comprises a polarizer configured to        selectively coupling light of a second polarization different        than said first polarization to said camera.    -   178. The system of any of Examples 158 to 169, wherein said        second out-coupling optical element is polarization selective,        selectively outcoupling light of said second polarization from        said at least one waveguide.    -   179. The system of any of the Examples above, wherein no        polarization selective optical elements that selectively direct        said second polarization in comparison to said first        polarization to said at least one camera are not included in the        path between the first coupling optical element and said at        least one camera receiving light therefrom.    -   180. The system of any of the Examples above, wherein said first        coupling optical element is not a polarization selective coupler        that selectively couples said second polarization in comparison        to said first polarization into said at least one waveguide.    -   181. The system of any of the Examples above, wherein the first        out-coupling optical element polarization is not a selective        coupling optical elements that selectively couples said second        polarization in comparison to said first polarization to said at        least one camera.    -   182. The system of any of the Examples above, wherein no        polarization selective optical elements that selectively direct        said second polarization in comparison to said first        polarization to said at least one camera are included in the        path between the first out-coupling optical element and said at        least one camera receiving light therefrom.    -   183. The system of any of the Examples above, wherein no        polarization selective optical elements that selectively direct        said second polarization in comparison to said first        polarization to said at least one camera are included in the        path between the first coupling optical element and said first        out-coupling optical element.    -   184. The system of any of the Examples above, wherein and an        optical element having optical power is disposed with respect to        said first coupling optical element such that propagation of        light coupled into said first coupling optical element is        altered by said optical power or said first coupling optical        element has optical power.    -   185. The system of any of Examples above, wherein an optical        element having optical power is disposed in an optical path to        said first coupling optical element such that light coupled into        said waveguide passes through said optical element having        optical power or said first coupling optical element has optical        power.    -   186. The system of any of Examples above, wherein an optical        element having optical power is disposed in an optical path from        said eye to said first coupling optical element such that light        from said eye coupled into said waveguide passes through said        optical element having optical power or said first coupling        optical element has optical power.    -   187. The system of any of the Examples above, wherein an optical        element having optical power is not disposed in an optical path        from the eye to said second coupling optical element.    -   188. The system of any of the Examples above, wherein an optical        element having optical power is not disposed with respect to        said second coupling optical element such that the propagation        of light to said second coupling optical element is not altered        by an optical element having optical power.    -   189. The system of any of Examples above, wherein said second        coupling optical element does not have optical power.    -   190. The system of any of the Examples above, wherein said        system is configured such that said light from said first        coupling element forms an image of an anterior surface of the        eye on said at least one camera thereby enabling images of said        anterior surface to be captured.    -   191. The system of any of the Examples above, wherein said        system is configured such that said light from said first        coupling optical element forms an image of glint on said at        least one camera thereby enabling images of said glint to be        captured.    -   192. The system of any of the Examples above, wherein said        system is configured such that said light from said second        coupling optical element forms an image of the retina on said at        least one camera thereby enabling images of said retina to be        captured.    -   193. The system of any of the Examples above, wherein said        system is configured such that light from said first coupling        optical element preferentially enabling images of glint to be        captured by said at least one camera and light from said second        coupling optical element preferentially enables images of the        retina to be captured by said at least one camera.    -   194. The system of any of the Examples above, wherein said        system is configured such that light from said first coupling        optical element preferentially enabling images of an anterior        surface of the eye to be captured by said at least one camera        and light from said second coupling optical element        preferentially enables images of the retina to be captured by        said at least one camera.    -   195. The system of any of the Examples above, wherein said        system is configured such that light from said first coupling        optical element preferentially enabling images of a corneal        surface to be captured by said at least one camera and light        from said second coupling optical element preferentially enables        images of the retina to be captured by said at least one camera.    -   196. The system of any of the Examples above, wherein said first        and second coupling optical elements are in contact with each        other.    -   197. The system of any of the Examples above, wherein said at        least one coupling optical element comprises a diffractive        optical element having a coupling area for coupling light into        said waveguide, said coupling area having an average thickness        in a range from 0.1 to 3 millimeters across, and wherein the        light is coupled into said waveguide via the coupling area of        the coupling element.    -   198. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.5        to 2 millimeters.    -   199. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 1 to        2 millimeters.    -   200. The system of any of the Examples above, wherein said        coupling area is slit shaped.    -   201. The system of any of the Examples above, wherein said        coupling area has a rectangular shape.    -   202. The system of any of the Examples above, wherein said        coupling area has an arcuate shape.    -   203. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 5 to 100.    -   204. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 10 to 100.    -   205. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 15 to 100.    -   206. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 20 and 100.    -   207. The system of any of the Examples above, wherein said        out-coupling optical element comprises a diffractive optical        element.    -   208. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 0.5 mm to 3.0 millimeters.    -   209. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters.    -   210. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        0.5 mm to 3.0 millimeters across in two orthogonal directions.    -   211. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        1.0 mm to 2.5 millimeters across in two orthogonal directions.    -   212. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio in a range from 1 to 2.    -   213. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio in a range from 1 to 1.75.    -   214. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.5.    -   215. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.3.    -   216. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.2.    -   217. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.1.    -   218. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said at least one camera.    -   219. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from an anterior portion of the eye of the user        wearing the head mounted display system is coupled into said        waveguide and guided therein such that images of said eye may be        captured by said camera such that said at least one camera can        capture images of said anterior portion of said eye.    -   220. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from a corneal surface of said eye of the user wearing        the head mounted display system is coupled into said waveguide        and guided therein such that images of said eye may be captured        by said camera such that said at least one camera can capture        images of said corneal surface of said eye.    -   221. The system of any of the Examples above, wherein the        coupling optical element has optical power.    -   222. The system of any of the Examples above, wherein the        optical power of the coupling optical element is configured to        increase collimation of light reflected from the eye that is        coupled into the waveguide to be guided to the camera.    -   223. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured to        increase collimation of light reflected from an anterior portion        of the eye that is coupled into the waveguide to be guided to        the camera.    -   224. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured to        increase collimation of light reflected from the cornea of the        eye that is coupled into the waveguide to be guided to the        camera.    -   225. The system of any of Examples above, wherein the optical        power comprises positive optical power.    -   226. The system of any of Examples above, wherein the optical        power corresponds to a focal length of in a range from 15 mm and        25 mm.    -   227. The system of any of Examples above, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said at        least one of said at least one waveguide out thereof such that        image content can be viewed by the user's eye.    -   228. The system of any of Examples above, wherein said at least        one image content out-coupling optical element and said at least        one coupling optical element are disposed laterally with respect        to each other.    -   229. The system of any of Example 228, wherein said at least one        image content out-coupling optical element is disposed more        nasally than said at least one out-coupling element.    -   230. The system of any of Example 228, wherein said at least one        image content out-coupling optical element is disposed more        temporally than said at least one out-coupling element.    -   231. The system of any of Examples above, wherein said at least        one coupling optical element comprises:        -   a first coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras;        -   and a second coupling optical element configured such that            light is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras,        -   wherein first coupling optical element and said second            coupling optical element are disposed laterally with respect            to each other.    -   232. The system of any of Example 92, wherein said first        coupling optical element comprising a diffractive optical        element having optical power.    -   233. The system of any of the Examples above, further comprising        a lens disposed with respect to said first coupling optical        element to provide optical power to light received by said first        coupling optical element.    -   234. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from the eye that is coupled into the waveguide to be        guided to the camera.    -   235. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from an anterior portion of the eye that is coupled        into the waveguide to be guided to the camera.    -   236. The system of any of the Examples above, wherein said        optical power is configured increase collimation of light        reflected from the cornea of the eye that is coupled into the        waveguide to be guided to the camera.    -   237. The system of any of the Examples above, wherein the        optical power comprises positive optical power.    -   238. The system of any of the Examples above, wherein the        optical power corresponds to a focal length about the distance        of the eye to first coupling optical element.    -   239. The system of any of any the Examples above, wherein the        optical power corresponds to a focal length in a range from 15        mm to 25 mm.    -   240. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from an anterior portion of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of said anterior portion of said eye        may be captured by said camera.    -   241. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from a corneal surface of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of the corneal surface said eye may be        captured by said camera.    -   242. The system of any of the Examples above, wherein said        second coupling optical element is configured such that light        reflected from the retina of the eye of the user wearing the        head mounted display system is coupled into said waveguide and        guided therein such that images of the retina of said eye may be        captured by said camera.    -   243. The system of any of the Examples above, wherein said        second coupling optical element does not include optical power.    -   244. The system of any of the Examples above, wherein said        second coupling optical element does not include a lens in an        optical path between the eye and said second coupling optical        element.    -   245. The system of any of the Examples above, wherein at least        one coupling optical element is configured such that light is        coupled into said waveguide and guided therein, said at least        one coupling optical element comprising a diffractive optical        element having a slit shaped coupling area for coupling light        into said waveguide, and wherein the camera is disposed in an        optical path with respect to said at least one out-coupling        optical element to receive at least a portion of the light that        is coupled into said waveguide via the coupling area of the        coupling element.    -   246. The system of any of the Examples above, wherein said        coupling area has an average thickness of in a range from 0.5 to        3 millimeters.    -   247. The system of any of the Examples above, wherein said        coupling area has an average thickness in a range from 0.5 to 2        millimeters.    -   248. The system of any of the Examples above, wherein said        coupling area has an average thickness in a range from 1 to 2        millimeters.    -   249. The system of any of the Examples above, wherein said        coupling area has a rectangular shape.    -   250. The system of any of the Examples above, wherein said        coupling area has an arcuate shape.    -   251. The system of any of the Examples above, wherein said        coupling area has a non-arcuate shape.    -   252. The system of any of the Examples above, wherein said        coupling area that has a length and a width, the length longer        than the width and said coupling area is straight along said the        length.    -   253. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 5 to 100.    -   254. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 10 to 100.    -   255. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 15 to 100.    -   256. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 20 to 100.    -   257. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a thickness from mm to 3.0        millimeters across.    -   258. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters across.    -   259. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension along one        direction of in a range from 0.5 mm to 3.0 millimeters across in        two orthogonal dimensions.    -   260. The system of any of the Examples above, wherein said        out-coupling optical element has an coupling area having a        dimension along one direction in a range from 1.0 mm to 2.5        millimeters across in two orthogonal dimensions.    -   261. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 2.    -   262. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.75.    -   263. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.5.    -   264. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.3.    -   265. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.2.    -   266. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.1.    -   267. The system of any of the Examples above, said at least one        out-coupling element has a coupling area for coupling light out        of said waveguide that is not a slit.    -   268. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.3 millimeters.    -   269. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 2 millimeters.    -   270. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 1.5 millimeters.    -   271. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 1 millimeters.    -   272. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 2 millimeters.    -   273. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 2 millimeters.    -   274. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 1.5 millimeters.    -   275. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 1 millimeters.    -   276. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 1.5 millimeters.    -   277. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 1 millimeters.    -   278. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.5 millimeters.    -   279. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.8 millimeters.    -   280. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.5 millimeters.    -   281. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.8 millimeters.    -   282. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.2 millimeters.    -   283. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.3 millimeters.    -   284. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.3 millimeters.    -   285. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 0.5 millimeters.    -   286. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 0.8 millimeters.    -   287. The system of any of the Examples above, wherein said        coupling area has a length of from 20 mm to 50 mm.    -   288. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 40 mm.    -   289. The system of any of the Examples above, wherein said        coupling area has a length of from 2 mm to 20 mm.    -   290. The system of any of the Examples above, wherein said        coupling area has a length of from 5 mm to 20 mm.    -   291. The system of any of the Examples above, wherein said        coupling area has a length of from 1 mm to 10 mm.    -   292. The system of any of the Examples above, wherein said        coupling area has a length of from 0.5 mm to 2 mm.    -   293. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 20 mm.    -   294. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 30 mm.    -   295. The system of any of the Examples above, wherein said        coupling area has a length of from 6 mm to 18 mm.    -   296. The system of any of Examples above, wherein the optical        power corresponds to a focal length of between 10 mm and 30 mm.    -   297. The system of any of the Examples above, wherein said        out-coupling optical element is polarization selective,        preferentially filtering out light of said first polarization as        compared to said second polarization.    -   298. The system of any of the Examples above, wherein said        out-coupling optical element is polarization selective,        preferentially coupling out light of said second polarization as        compared to said first polarization.    -   299. The system of any of the Examples above, wherein said        system is configured such that light coupled into said waveguide        by said first coupling optical element is acted on by a first        total optical power and light coupled into said waveguide by        said second coupling optical element is acted on by a second        total optical power and said first total optical power is larger        than said second total optical power.    -   300. The system of any of the Examples above, wherein said first        coupling optical element has a first optical power and said        second coupling optical element has a second optical power, and        said first optical power is larger than said second optical        power.    -   301. The system of any of the Examples above, wherein said first        coupling optical element has a first lens associated therewith        having has a first optical power and said second coupling        optical element has associated therewith a second lens having a        second optical power, and said first optical power is larger        than said second optical power.

Example Section V

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   at least one camera;        -   at least one waveguide;        -   at least one coupling optical element configured such that            light is coupled into said waveguide and guided therein,            said at least one coupling optical element comprising a            diffractive optical element having an coupling area for            coupling light into said waveguide, said coupling area            having an average thickness in a range from 0.1 to 3            millimeters across; and        -   at least one out-coupling element configured to couple light            guided within said waveguide out of said waveguide and            direct said light to said camera,        -   wherein at least one camera is disposed in an optical path            with respect to said at least one out-coupling optical            element to receive at least a portion of the light that is            coupled into said waveguide via the coupling area of the at            least one coupling optical element and guided therein and            that is coupled out from said waveguide by said at least one            outcoupling element such that images may be captured by said            camera.    -   2. The system of any of the Examples above, wherein said average        thickness of said coupling area is in a range from 0.5 to 2        millimeters.    -   3. The system of any of the Examples above, wherein said average        thickness of said coupling area is in a range from 1 to 2        millimeters.    -   4. The system of any of the Examples above, wherein said        coupling area is slit shaped.    -   5. The system of any of the Examples above, wherein said        coupling area has a rectangular shape.    -   6. The system of any of the Examples above, wherein said        coupling area has an arcuate shape.    -   7. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 5 to 100.    -   8. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 10 to 100.    -   9. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 15 to 100.    -   10. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 20 and 100.    -   11. The system of any of the Examples above, wherein said        out-coupling optical element comprises a diffractive optical        element.    -   12. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 0.5 mm to 3.0 millimeters.    -   13. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters.    -   14. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        0.5 mm to 3.0 millimeters across in two orthogonal directions.    -   15. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension in a range from        1.0 mm to 2.5 millimeters across in two orthogonal directions.    -   16. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio in a range from 1 to 2.    -   17. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio in a range from 1 to 1.75.    -   18. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.5.    -   19. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.3.    -   20. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.2.    -   21. The system of any of the Examples above, wherein said        coupling area of said out-coupling optical element has an aspect        ratio of in a range from 1 to 1.1.    -   22. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said at least one camera.    -   23. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from an anterior portion of the eye of the user        wearing the head mounted display system is coupled into said        waveguide and guided therein such that images of said eye may be        captured by said camera such that said at least one camera can        capture images of said anterior portion of said eye.    -   24. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from a corneal surface of said eye of the user wearing        the head mounted display system is coupled into said waveguide        and guided therein such that images of said eye may be captured        by said camera such that said at least one camera can capture        images of said corneal surface of said eye.    -   25. The system of any of the Examples above, wherein the        coupling optical element has optical power.    -   26. The system of any of the Examples above, wherein the optical        power of the coupling optical element is configured to increase        collimation of light reflected from the eye that is coupled into        the waveguide to be guided to the camera.    -   27. The system of any of the Examples above, wherein the optical        power of said coupling optical element is configured to increase        collimation of light reflected from an anterior portion of the        eye that is coupled into the waveguide to be guided to the        camera.    -   28. The system of any of the Examples above, wherein the optical        power of said coupling optical element is configured to increase        collimation of light reflected from the cornea of the eye that        is coupled into the waveguide to be guided to the camera.    -   29. The system of any of Examples above, wherein the optical        power comprises positive optical power.    -   30. The system of any of Examples above, wherein the optical        power corresponds to a focal length of in a range from 15 mm and        25 mm.    -   31. The system of any of Examples above, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said at        least one of said at least one waveguide out thereof such that        image content can be viewed by the user's eye.    -   32. The system of any of Examples above, wherein said at least        one image content out-coupling optical element and said at least        one coupling optical element are disposed laterally with respect        to each other.    -   33. The system of any of Example 32, wherein said at least one        image content out-coupling optical element is disposed more        nasally than said at least one out-coupling element.    -   34. The system of any of Example 32, wherein said at least one        image content out-coupling optical element is disposed more        temporally than said at least one out-coupling element.    -   35. The system of any of Examples above, wherein said at least        one coupling optical element comprises:        -   a first coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras; and        -   a second coupling optical element configured such that light            is coupled into said at least one waveguide and guided            therein to at least one of said at least one cameras,        -   wherein first coupling optical element and said second            coupling optical element are disposed laterally with respect            to each other.    -   36. The system of any of Example 35, wherein said first coupling        optical element comprising a diffractive optical element having        optical power.    -   37. The system of any of the Examples above, further comprising        a lens disposed with respect to said first coupling optical        element to provide optical power to light received by said first        coupling optical element.    -   38. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from the eye that is coupled into the waveguide to be        guided to the camera.    -   39. The system of any of the Examples above, wherein said        optical power is configured to increase collimation of light        reflected from an anterior portion of the eye that is coupled        into the waveguide to be guided to the camera.    -   40. The system of any of the Examples above, wherein said        optical power is configured increase collimation of light        reflected from the cornea of the eye that is coupled into the        waveguide to be guided to the camera.    -   41. The system of any of the Examples above, wherein the optical        power comprises positive optical power.    -   42. The system of any of the Examples above, wherein the optical        power corresponds to a focal length about the distance of the        eye to first coupling optical element.    -   43. The system of any of any the Examples above, wherein the        optical power corresponds to a focal length in a range from 15        mm to 25 mm.    -   44. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from an anterior portion of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of said anterior portion of said eye        may be captured by said camera.    -   45. The system of any of the Examples above, wherein said first        coupling optical element is configured such that light reflected        from a corneal surface of the eye of the user wearing the head        mounted display system is coupled into said waveguide and guided        therein such that images of the corneal surface said eye may be        captured by said camera.    -   46. The system of any of the Examples above, wherein said second        coupling optical element is configured such that light reflected        from the retina of the eye of the user wearing the head mounted        display system is coupled into said waveguide and guided therein        such that images of the retina of said eye may be captured by        said camera.    -   47. The system of any of the Examples above, wherein said second        coupling optical element does not include optical power.    -   48. The system of any of the Examples above, wherein said second        coupling optical element does not include a lens in an optical        path between the eye and said second coupling optical element.    -   49. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   at least one camera;        -   at least one waveguide;        -   at least one coupling optical element configured such that            light is coupled into said waveguide and guided therein,            said at least one coupling optical element comprising a            diffractive optical element having a slit shaped coupling            area for coupling light into said waveguide; and        -   at least one out-coupling element configured to couple light            guided within said waveguide out of said waveguide and            direct said light to said camera,        -   wherein the camera is disposed in an optical path with            respect to said at least one out-coupling optical element to            receive at least a portion of the light that is coupled into            said waveguide via the coupling area of the at least one            coupling optical element and guided therein and that is            coupled out from said waveguide by said at least one            outcoupling element such that images may be captured by said            camera.    -   50. The system of any of the Examples above, wherein said        coupling area has an average thickness of in a range from 0.5 to        3 millimeters.    -   51. The system of any of the Examples above, wherein said        coupling area has an average thickness in a range from 0.5 to 2        millimeters.    -   52. The system of any of the Examples above, wherein said        coupling area has an average thickness in a range from 1 to 2        millimeters.    -   53. The system of any of the Examples above, wherein said        coupling area has a rectangular shape.    -   54. The system of any of the Examples above, wherein said        coupling area has an arcuate shape.    -   55. The system of any of the Examples above, wherein said        coupling area has a non-arcuate shape.    -   56. The system of any of the Examples above, wherein said        coupling area that has a length and a width, the length longer        than the width and said coupling area is straight along said the        length.    -   57. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 5 to 100.    -   58. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 10 to 100.    -   59. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 15 to 100.    -   60. The system of any of the Examples above, wherein said        coupling area has an aspect ratio in a range from 20 to 100.    -   61. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a thickness from mm to 3.0        millimeters across.    -   62. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having an average thickness in a        range from 1 mm to 2.5 millimeters across.    -   63. The system of any of the Examples above, wherein said        out-coupling optical element has a coupling area for coupling        light out of said waveguide having a dimension along one        direction of in a range from 0.5 mm to 3.0 millimeters across in        two orthogonal dimensions.    -   64. The system of any of the Examples above, wherein said        out-coupling optical element has an coupling area having a        dimension along one direction in a range from 1.0 mm to 2.5        millimeters across in two orthogonal dimensions.    -   65. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 2.    -   66. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.75.    -   67. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.5.    -   68. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.3.    -   69. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.2.    -   70. The system of any of the Examples above, wherein said at        least one out-coupling optical element has a coupling area for        coupling light out of said waveguide having an aspect ratio in a        range from 1 to 1.1.    -   71. The system of any of the Examples above, said at least one        out-coupling element has a coupling area for coupling light out        of said waveguide that is not a slit.    -   72. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.3 millimeters.    -   73. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 2 millimeters.    -   74. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 1.5 millimeters.    -   75. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 1 millimeters.    -   76. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 2 millimeters.    -   77. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 2 millimeters.    -   78. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 1.5 millimeters.    -   79. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 1 millimeters.    -   80. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 1.5 millimeters.    -   81. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 1 millimeters.    -   82. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.5 millimeters.    -   83. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.8 millimeters.    -   84. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.5 millimeters.    -   85. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.8 millimeters.    -   86. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.2 millimeters.    -   87. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.1        to 0.3 millimeters.    -   88. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.2        to 0.3 millimeters.    -   89. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 0.5 millimeters.    -   90. The system of any of the Examples above, wherein said        average thickness of said coupling area is in a range from 0.3        to 0.8 millimeters.    -   91. The system of any of the Examples above, wherein said        coupling area has a length of from 20 mm to 50 mm.    -   92. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 40 mm.    -   93. The system of any of the Examples above, wherein said        coupling area has a length of from 2 mm to 20 mm.    -   94. The system of any of the Examples above, wherein said        coupling area has a length of from 5 mm to 20 mm.    -   95. The system of any of the Examples above, wherein said        coupling area has a length of from 1 mm to 10 mm.    -   96. The system of any of the Examples above, wherein said        coupling area has a length of from 0.5 mm to 2 mm.    -   97. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 20 mm.    -   98. The system of any of the Examples above, wherein said        coupling area has a length of from 10 mm to 30 mm.    -   99. The system of any of the Examples above, wherein said        coupling area has a length of from 6 mm to 18 mm.    -   100. The system of any of the Examples above, wherein at least        one coupling optical element is configured such that light is        coupled into said waveguide and guided therein, said at least        one coupling optical element comprising a diffractive optical        element having optical power, and wherein the camera is disposed        in an optical path with respect to said at least one        out-coupling optical element to receive at least a portion of        the light that is coupled into said waveguide via the coupling        optical element.    -   101. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said at least one camera.    -   102. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from an anterior portion of the eye of the user        wearing the head mounted display system is coupled into said        waveguide and guided therein such that images of said eye may be        captured by said camera such that said at least one camera can        capture images of said anterior portion of said eye.    -   103. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from a corneal surface of said eye of the user wearing        the head mounted display system is coupled into said waveguide        and guided therein such that images of said eye may be captured        by said camera such that said at least one camera can capture        images of said corneal surface of said eye.    -   104. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured to        increase collimation of light reflected from the eye that is        coupled into the waveguide to be guided to the camera.    -   105. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured to        increase collimation of light reflected from an anterior portion        of the eye that is coupled into the waveguide to be guided to        the camera.    -   106. The system of any of the Examples above, wherein the        optical power of said coupling optical element is configured        increase collimation of light reflected from the cornea of the        eye that is coupled into the waveguide to be guided to the        camera.    -   107. The system of any of Examples above, wherein the optical        power comprises positive optical power.    -   108. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the retina of the eye of the user wearing the        head mounted display system is coupled into said waveguide and        guided therein such that images of said retina may be captured        by said camera.    -   109. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   110. The system of Example 109, wherein said eyepiece is        configured to receive light from said image projector and to        direct said light into said user's eye to display augmented        reality image content to the user's vision field.    -   111. The system of any of Examples 109-110, wherein said        eyepiece comprises said at least one waveguide.    -   112. The system of any of Examples 109-111, wherein said image        projector is configured to direct light into an edge of said        eyepiece.    -   113. The system of Examples 111 or 112, wherein said image        projector is configured to direct light into an edge of said at        least one waveguide.    -   114. The system of any of the Examples above, further comprising        at least one in-coupling optical element configured to in-couple        light from said image projector into said at least one waveguide        so as to guide light from said image projector for providing        said image content to said user's eye.    -   115. The system of any of Examples above, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said        waveguide out of said at least one waveguide such that image        content can be viewed by the user's eye.    -   116. The system of any of the Examples above, wherein said at        least one coupling optical element faces the eye of the user        wearing the head mounted imaging system to receive light from        said eye.    -   117. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        from the environment in front of the user wearing the head        mounted imaging system is coupled into said at least one        waveguide and guided therein such that images of said        environment may be captured by said camera.    -   118. The system of any of the Examples above, wherein said at        least one coupling optical element faces the environment in        front of the user wearing the head mounted imaging system to        receive light from said environment.    -   119. The system of Example 118, wherein said at least one        coupling optical element is configured such that light is        coupled into a first waveguide and guided therein to said camera        and said at least one image content out-coupling optical element        is configured to couple light from said image projector guided        within a second waveguide out of said second waveguide.    -   120. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        is coupled into a first waveguide and guided therein to said        camera and said image projector is configured to couple light        into a second waveguide to provide image content to said eye.    -   121. The system of any of the Examples above, wherein said image        projector comprises a light source, a modulator, and projection        optics.    -   122. The system of any of the Examples above, wherein the image        projector comprises scanning optical fiber.    -   123. The system of any of Examples 122, wherein the modulator        comprises a light modulator.    -   124. The system of Example 123, wherein the light modulator        comprises a spatial light modulator.    -   125. The system of any of the Examples above, wherein said        camera comprises a detector array and imaging optics.    -   126. The system of Example 125, wherein said imaging optics is        configured to focus collimated light onto said detector array.    -   127. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        visible light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   128. The system of any of the Examples above, wherein said at        least one waveguide comprises material that is transparent to        infrared light having a refractive index sufficient to guide        light in said waveguide by total internal reflection.    -   129. The system of any of the Examples above, wherein said at        least one waveguide comprises a stack of waveguides.    -   130. The system of any of the Examples above, wherein different        waveguides of the stack of waveguides are configured to output        light with different wavefront divergence as if projected from        different distances from the user's eye.    -   131. The system of any of the Examples above, wherein different        waveguides of the stack of waveguides are configured to output        light with different colors.    -   132. The system of any of the Examples above, wherein different        waveguides comprise first, second, and third waveguides, said        system is configured such that the first is for red color light,        the second for is green color light, and the third is for blue        color light.    -   133. The system of any of the Examples above, wherein the at        least one in-coupling optical element comprises a diffractive        optical element.    -   134. The system of any of the Examples above, wherein the at        least one in-coupling optical element comprises a diffraction        grating.    -   135. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization selective turning        element.    -   136. The system of any of the Examples above, wherein the        in-coupling element comprises a polarization grating.    -   137. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization selective        turning element.    -   138. The system of any of the Examples above, wherein the at        least one coupling element comprises a polarization grating.    -   139. The system of any of the Examples above, wherein the        coupling optical element comprises liquid crystal.    -   140. The system of any of the Examples above, wherein the        coupling optical element comprises a liquid crystal polarization        grating.    -   141. The system of any of the Examples above, wherein the        out-coupling optical element comprises a diffractive optical        element.    -   142. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization        selective turning element.    -   143. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a polarization grating.    -   144. The system of any of the Examples above, wherein the at        least one out-coupling element comprises liquid crystal.    -   145. The system of any of the Examples above, wherein the at        least one out-coupling element comprises a liquid crystal        polarization grating.    -   146. The system of any of the Examples above, wherein the at        least one out-coupling element comprises an off-axis reflector.    -   147. The system of any of the Examples above, wherein the same        waveguide (a) guides light coupled from the user's eye into said        at least one waveguide to be received by said camera so as to        capture an image of at least a portion of the eye of the user,        and (b) guides light coupled from said image projector such that        light from said projector can be directed to said user's eye        such that said image from said image projector is in the vision        field of said the user.    -   148. The system of any of the Examples above, wherein said        system is configured to perform eye tracking based images of        said eye.    -   149. The system of Example 148, wherein performing eye tracking        based on said images of said eye comprises storing an image of        the retina of said eye.    -   150. The system of any of any of the Examples above, wherein        said system is configured to:        -   obtain an image of a portion of said retina of said eye            using said camera;        -   compare one or more stored images of said retina with the            image of said portion of said retina; and        -   determine a gaze of the user based on the comparison of the            one or more stored images and the image of the portion of            the retina obtained from the camera.    -   151. The system of Example 150, wherein determining a gaze of        the user comprises determining to which portion of the retina        corresponds to the image of said portion of the retina.    -   152. The system of any of the Examples above, wherein        determining a gaze of the user comprises determining an        orientation of the eye.    -   153. The system of any of the Examples above, wherein said        system is configured to obtain biometric data based on one or        more images of the user's eye obtained with said camera.    -   154. The system of any of the Examples above, wherein said        system is configured to identify the user via biometric sensing        based on one or more images of said eye obtained with said        camera.    -   155. The system of any of the above Examples, wherein said        system is configured to provide illumination of a first        polarization and to preferentially capture images with said        camera using light of a second polarization different than said        first polarization.    -   156. The system of any of the above Examples, wherein said        system is configured to illuminate said user's eye with light of        a first polarization and to preferentially capture images of        said user's eye with said camera using light of a second        polarization different than said first polarization.    -   157. The system of any of the Examples above, wherein said first        and second polarizations are orthogonal.    -   158. The system of any of the above Examples, further comprising        a light source disposed so as to provide illumination so as to        capture images with said camera.    -   159. The system of any of the above Examples, further comprising        a light source disposed so as to illuminate of the user's eye.    -   160. The system of any of the Examples above, wherein said light        source comprises one or more infrared light sources.    -   161. The system of any of the Examples above, wherein said light        source comprises one or more infrared light emitting diodes        (LEDs).    -   162. The system of any of the Examples above, wherein said light        source is pulsed.    -   163. The system of any of the Examples above, wherein said light        source is configured to input light into a waveguide to provide        said illumination.    -   164. The system of any of the Examples above, wherein said light        source is configured to input light into a waveguide disposed        with respect to said eye to provide illumination to said eye.    -   165. The system of any of the Examples above, further comprising        an illumination in-coupling optical element configured to couple        light from said light source into said waveguide.    -   166. The system of any of the Examples above, wherein said light        source is configured to input light into said at least one        waveguide to provide illumination.    -   167. The system of any of the Examples above, wherein said light        source is configured to input light into the same waveguide as        used to project image content to the user's eye.    -   168. The system of any of the Examples above, wherein said light        source is configured, to provide illumination to the user's eye,        to input light into the same waveguide as used to guide light to        the camera.    -   169. The system of any of the Examples above, wherein said light        source is configured to input light into the same waveguide as        used to guide light from the user's eye to the camera.    -   170. The system of any of the Examples above, further comprising        an illumination in-coupling optical element configured to couple        light from said light source into said waveguide to provide        illumination.    -   171. The system of any of the Examples above, wherein said        illumination in-coupling optical element is polarization        selective, in-coupling light of a first polarization.    -   172. The system of any of the Examples above, wherein said light        source is a polarized light source configured to output        polarized light having a first polarization.    -   173. The system of any of the Examples above, wherein said light        source is configured to direct polarized light having a first        polarization onto said eye.    -   174. The system of any of the Examples above, further comprising        an illumination polarizer having a first polarization disposed        in the optical path between said light source and said eye to        polarize light directed to said eye.    -   175. The system of any of the Examples above, wherein the        illumination polarizer is disposed in the optical path between        said light source and said waveguide configured to provide        illumination.    -   176. The system of any of the Examples above, further comprising        an image acquisition polarizer in an optical path between said        eye and said camera.    -   177. The system of any of the Examples above, wherein said image        acquisition polarizer is proximal said camera.    -   178. The system of any of the Examples above, wherein said image        acquisition polarizer is disposed in an optical path between (a)        said at least one waveguide configured guide light to said        camera and (b) said camera.    -   179. The system of any of the Examples above, wherein said image        acquisition polarizer reduces the amount of light of said first        polarization that reaches said camera.    -   180. The system of any of the Examples above, wherein said image        acquisition polarizer comprises a polarizer configured to        selectively coupling light of a second polarization different        than said first polarization to said camera.    -   181. The system of any of the Examples above, further comprising        at least one light consolidating element disposed in an optical        path between said at least one coupling element and said at        least one out-coupling optical element to reduce lateral spatial        extent of light from said at least one coupling element prior to        reaching said at least one out-coupling optical element.    -   182. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a diffractive        optical element.    -   183. The system of any of the Examples above, wherein said at        least one light consolidating element comprises a hologram or        diffraction grating.    -   184. The system of any of Examples 183, wherein the one or more        stored images of the retina of the eye comprise a composite        image of the retina of the eye generated using a plurality of        images of different portions of the retina of the eye.    -   185. The system of any of the Examples above, wherein the        composite image of the retina comprises a plurality of images of        the retina stitched together.    -   186. The system of any of the Examples above, wherein the        plurality of images of the retina stitched together comprises        images obtained when a fixation target was displayed in the        vision field of the user at various locations, respectively.    -   187. The system of any of the Examples above, wherein the one or        more stored images of the retina comprises images obtained when        a fixation target was displayed in the vision field of the user        at various locations, respectively.    -   188. The system of any of the Examples above, wherein the system        is further configured to use the obtained image of the portion        of the retina of the eye to update the composite image.    -   189. The system of any of the Examples above, wherein using the        obtained image of the portion of the retina to update the        composite image of the retina comprises stitching the obtained        image into a section of the composite image corresponding to the        portion of the retina shown in the obtained image.    -   190. The system of any of the Examples above, wherein the system        is further configured to apply a digital filter to the obtained        image of the portion of the retina of the eye to obtain a        filtered image of the portion of the retina.    -   191. The system of any of the Examples above, wherein the system        is further configured to compare one or more stored images of        the retina with the filtered image of the portion of the retina.    -   192. The system of any of the Examples above, wherein the        digital filter comprises a Frangi Filter.    -   193. The system of any of the Examples above, wherein the system        is configured to apply edge enhance the obtained image of the        portion of the retina.    -   194. The system of any of the Examples above, wherein said        system is configured to perform user identification verification        using images of the retina.    -   195. The system of any of the Examples above, wherein said        system is configured to:        -   obtain an image of a portion of said retina of said eye            using said camera;        -   compare one or more stored images of said retina with the            image of said portion of said retina.    -   196. The system of any of the Examples above, wherein the one or        more stored images of the retina of the eye comprise a composite        image of the retina of the eye generated using a plurality of        images of different portions of the retina of the eye.    -   197. The system of any of the Examples above, wherein the        composite image of the retina comprises a plurality of images of        the retina stitched together.    -   198. The system of any of the Examples above, wherein the        plurality of images of the retina stitched together comprises        images obtained when a fixation target was displayed in the        vision field of the user at various locations, respectively.    -   199. The system of any of the Examples above, wherein the one or        more stored images of the retina comprises images obtained when        a fixation target was displayed in the vision field of the user        at various locations, respectively.    -   200. The system of any of the Examples above, wherein the system        is further configured to use the obtained image of the portion        of the retina of the eye to update the composite image.    -   201. The system of any of the Examples above, wherein using the        obtained image of the portion of the retina to update the        composite image of the retina comprises stitching the obtained        image into a section of the composite image corresponding to the        portion of the retina shown in the obtained image.    -   202. The system of any of the Examples above, wherein the system        is further configured to apply a digital filter to the obtained        image of the portion of the retina of the eye to obtain a        filtered image of the portion of the retina.    -   203. The system of any of the Examples above, wherein the system        is further configured to compare one or more stored images of        the retina with the filtered image of the portion of the retina.    -   204. The system of any of the Examples above, wherein the        digital filter comprises a Frangi Filter.    -   205. The system of any of the Examples above, wherein the system        is configured to apply edge enhancement the obtained image of        the portion of the retina.    -   206. The system of any of the Examples above, wherein the        optical power corresponds to a focal length about the distance        of the eye to the coupling optical element.    -   207. The system of any of the Examples above, wherein the        optical power corresponds to a focal length of between 15 mm and        25 mm.    -   208. The system of any of the Examples above, wherein the        optical power corresponds to a focal length of between 10 mm and        30 mm.    -   209. The system of any of the Examples above, wherein said        out-coupling optical element is polarization selective,        preferentially filtering out light of said first polarization as        compared to said second polarization.    -   210. The system of any of the Examples above, wherein said        out-coupling optical element is polarization selective,        preferentially coupling out light of said second polarization as        compared to said first polarization.    -   211. The system of any of the Examples above, wherein said        system is configured such that light coupled into said waveguide        by said first coupling optical element is acted on by a first        total optical power and light coupled into said waveguide by        said second coupling optical element is acted on by a second        total optical power and said first total optical power is larger        than said second total optical power.    -   212. The system of any of the Examples above, wherein said first        coupling optical element has a first optical power and said        second coupling optical element has a second optical power, and        said first optical power is larger than said second optical        power.    -   213. The system of any of the Examples above, wherein said first        coupling optical element has a first lens associated therewith        having has a first optical power and said second coupling        optical element has associated therewith a second lens having a        second optical power, and said first optical power is larger        than said second optical power.

Example Section VI

-   -   1. A head-mounted system configured to image at least a portion        of an eye of a user wearing the head-mounted system, said        head-mounted system comprising:        -   a frame configured to be supported on a head of the user;        -   at least one camera; and        -   an eyepiece disposed on the frame, at least a portion of            said eyepiece being transparent and disposed at a location            in front of the user's eye when the user wears said            head-mounted system such that said transparent portion            transmits light from the environment in front of the user to            the user's eye to provide a view of the environment in front            of the user, said eyepiece comprising:            -   at least one waveguide;            -   at least two optical elements spaced a particular                distance apart, said at least two optical elements                comprising:                -   at least one coupling optical element configured                    such that light from the eye of the user wearing the                    head-mounted system is coupled into said waveguide                    and guided therein, said at least one coupling                    optical element comprising a coupling area for                    coupling light into said waveguide, said coupling                    area having at least one dimension measuring less                    than or equal to 2.5% of the particular distance;                    and                -   at least one out-coupling element configured to                    couple light guided within said waveguide out of                    said waveguide and direct said light to said camera,        -   wherein said at least one camera is disposed in an optical            path with respect to said at least one out-coupling optical            element to receive at least a portion of the light that is            coupled into said waveguide via the coupling area of the            coupling optical element and guided therein and that is            coupled out from said waveguide by said out-coupling            coupling element such that images may be captured by said            camera.    -   2. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        coupling optical element is less than or equal to 2% of the    -   3. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        coupling optical element is less than or equal to 1.5% of the        particular distance.    -   4. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        coupling optical element is less than or equal to 1% of the        particular distance.    -   5. The system of any of the Examples above, wherein said at        least one out-coupling element comprises a coupling area for        coupling light into said waveguide, said coupling area having at        least one dimension measuring less than or equal to 2.5% of the        particular distance.    -   6. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        out-coupling optical element is less than or equal to 2% of the        particular distance.    -   7. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        out-coupling optical element is less than or equal to 1.5% of        the particular distance.    -   8. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        out-coupling optical element is less than or equal to 1% of the        particular distance.    -   9. The system of any of the Examples above, wherein said        particular distance is substantially equal to the distance of        the eye to the coupling optical element.    -   10. The system of any of the Examples above, wherein said        particular distance is between and 30 millimeters.    -   11. The system of any of the Examples above, wherein said        particular distance is between 10 and 25 millimeters.    -   12. The system of any of the Examples above, wherein said at        least one coupling optical element comprises a diffractive        optical element.    -   13. The system of any of the Examples above, further comprising:        -   an image projector for projecting images into the user's eye            to display image content in the vision field of the user,            said image projector configured to input light into at least            one of said at least one waveguide to be guided therein;        -   at least one image content in-coupling optical element            configured to in-couple light from said image projector into            said at least one waveguide so as to guide light from said            image projector therein; and        -   at least one image content out-coupling optical element            configured to couple light from said image projector guided            within said at least one of said at least one waveguide out            thereof such that image content can be viewed by the user's            eye.

Example Section VII

-   -   1. A head-mounted system configured to image at least a portion        of an eye of a user wearing the head-mounted system, said        head-mounted system comprising:        -   a frame configured to be supported on a head of the user;        -   at least one camera; and        -   an eyepiece disposed on the frame, at least a portion of            said eyepiece being transparent and disposed at a particular            distance in front of the user's eye when the user wears said            head-mounted system such that said transparent portion            transmits light from the environment in front of the user to            the user's eye to provide a view of the environment in front            of the user, said eyepiece comprising:            -   at least one waveguide;            -   at least one coupling optical element configured such                that light from the eye of the user wearing the                head-mounted system is coupled into said waveguide and                guided therein, said at least one coupling optical                element comprising a coupling area for coupling light                into said waveguide, said coupling area having at least                one dimension measuring less than or equal to 2.5% of                the particular distance; and            -   at least one out-coupling element configured to couple                light guided within said waveguide out of said waveguide                and direct said light to said camera,        -   wherein said at least one camera is disposed in an optical            path with respect to said at least one out-coupling optical            element to receive at least a portion of the light that is            coupled into said waveguide via the coupling area of the            coupling optical element and guided therein and that is            coupled out from said waveguide by said out-coupling            coupling element such that images may be captured by said            camera.    -   2. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        coupling optical element is less than or equal to 2% of the        particular distance.    -   3. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        coupling optical element is less than or equal to 1.5% of the    -   4. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        coupling optical element is less than or equal to 1% of the        particular distance.    -   5. The system of any of the Examples above, wherein said at        least one out-coupling element comprises a coupling area for        coupling light into said waveguide, said coupling area having at        least one dimension measuring less than or equal to 2.5% of the        particular distance.    -   6. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        out-coupling optical element is less than or equal to 2% of the        particular distance.    -   7. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        out-coupling optical element is less than or equal to 1.5% of        the particular distance.    -   8. The system of any of the Examples above, wherein said at        least one dimension of said coupling area of said at least one        out-coupling optical element is less than or equal to 1% of the        particular distance.    -   9. The system of any of the Examples above, wherein said at        least one coupling optical element and said at least one        out-coupling optical element are spaced apart by a distance        substantially equal to the particular distance is substantially        equal to the distance of the eye to the coupling optical        element.    -   10. The system of any of the Examples above, wherein said        particular distance is between and 30 millimeters.    -   11. The system of any of the Examples above, wherein said        particular distance is between and 25 millimeters.    -   12. The system of any of the Examples above, wherein said at        least one coupling optical element comprises a diffractive        optical element.    -   13. The system of any of the Examples above, further comprising:        -   an image projector for projecting images into the user's eye            to display image content in the vision field of the user,            said image projector configured to input light into at least            one of said at least one waveguide to be guided therein;        -   at least one image content in-coupling optical element            configured to in-couple light from said image projector into            said at least one waveguide so as to guide light from said            image projector therein; and        -   at least one image content out-coupling optical element            configured to couple light from said image projector guided            within said at least one of said at least one waveguide out            thereof such that image content can be viewed by the user's            eye.

Example Section VIII

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   a transparent layer supported on said frame and disposed at            a location in front of the user's eye when the user wears            said head-mounted display such that said transparent layer            transmits light from an environment in front of the user to            the user's eye to provide a view of the environment in front            of the user;        -   at least one elongate light guide having a first end and a            second end, said first end disposed within said transparent            layer, said first end of said optical fiber having an output            for emitting light such that said light is directed to said            eye;        -   at least one camera disposed to receive at least a portion            of the light reflected from the eye to capture images using            light reflected from the user's eye.    -   2. The system of Example, 1, wherein said first end of said        elongate light guide includes an angled reflector configured to        couple light through said output of said elongate light guide.    -   3. The system of Example 2, wherein said angled reflector        comprises a beveled surface at said first end of said elongate        light guide.    -   4. The system of any of Examples 2 or 3, wherein said angled        reflector comprises a cleaved surface at said first end of said        elongate light guide.    -   5. The system of any of Examples 2 to 4, wherein said angled        reflector comprises metallization.    -   6. The system of any of Examples 2 to 5, wherein said angled        reflector comprises IR reflective coating.    -   7. The system of any of Examples 2 to 6, wherein said fiber        extends along a length within said transparent layer and said        angle reflector is oriented at an angle of from 35° and with        respect to said length of said fiber.    -   8. The system of any of Examples 2 to 7, wherein said        transparent layer has oppositely facing front and rear major        surfaces and said angle reflector is oriented at an angle of        from 35° and 55° with respect to said front and rear major        surfaces.    -   9. The system of any of the above Examples, wherein said        transparent layer comprises an index matching material disposed        between front and rear glass covers.    -   10. The system of any of the above Examples, wherein the        transparent layer comprises a channel configured to accept the        elongate light guide.    -   11. The system of any of the above Examples, wherein said        elongate light guide is disposed within a channel of the        transparent layer.    -   12. The system of any of the above Examples, wherein said second        end of said elongate light guide has an input for receiving        light, said elongate light guide configured such that light        received by said input of said elongate light guide at said        second end is guided within said elongate light guide to said        output at said first end of said elongate light guide.    -   13. The system of any of the above Examples, wherein said at        least one elongate light guide comprises an optical fiber        comprising a core and a cladding and said core is between 8 μm        and 110 μm across.    -   14. The system of any of the above Examples, wherein said at        least one elongate waveguide comprises an optical fiber        comprises a core and a cladding and said cladding is between 100        μm and 150 μm across.    -   15. The system of Example 14, wherein the cladding comprises 125        μm across.    -   16. The system of any of the above Examples, wherein said second        end of said elongate light guide extends outside of said        transparent layer such that said input for receiving light is        outside said transparent layer.    -   17. The system of any of the above Examples, wherein said at        least one elongate light guide comprises a plurality of elongate        light guides.    -   18. The system of any of the above Examples, wherein said        transparent layer has first and second sides and said at least        one elongate light guide comprises a first elongate light guide        embedded in said first side of said transparent layer and a        second elongate light guides embedded in said second side of        said transparent layer.    -   19. The system of any of the above Examples, wherein said        transparent layer has first and second sides and said at least        one elongate light guide comprises a first pair of elongate        light guides embedded in said first side of said transparent        layer and a second pair of elongate light guides embedded in        said second side of said transparent layer.    -   20. The system of Examples 18 or 19, wherein first and second        sides are nasal and temporal sides of said transparent layer.    -   21. The system of any of Examples 18 to 20, wherein first and        second sides are superior and inferior sides of said transparent        layer.    -   22. The system of any of the above Examples, wherein said output        of said elongate light guide creates a point source illuminating        said eye of the user.    -   23. The system of Examples 17-22, wherein said plurality of        elongate light guides each have outputs that create point        sources illuminating said eye of the user.    -   24. The system of Examples 17-23, wherein said first and second        pairs of elongate light guides each have outputs that create        point sources illuminating said eye of the user.    -   25. The system of any of the above Examples, further comprising        at least one light source, said at least one light source        optically coupled to said elongate light guides to inject light        therein such that light is output from said first end of said        elongate light guide.    -   26. The system of Example 25, wherein said at least one light        source comprises one or more infrared light sources.    -   27. The system of any of Examples 25 or 26, wherein said at        least one light source comprises one or more light emitting        diodes (LEDs) or lasers.    -   28. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   29. The system of Example 28, wherein said eyepiece is        configured to receive light from said image projector and to        direct said light into said user's eye to display augmented        reality image content to the user's vision field.    -   30. The system of Examples 28 or 29, wherein said eyepiece        comprises at least one waveguide.    -   31. The system of Example 30, wherein said image projector is        configured to direct light into said at least one waveguide.    -   32. The system of Examples 30 or 31 above, wherein said at least        one waveguide comprises a stack of waveguides.    -   33. The system of Example 32, wherein different waveguides of        the stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   34. The system of Example 32 or 33, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   35. The system of any of the Examples 28 to 34, wherein said        transparent layer comprises a layer in said eyepiece.    -   36. The system of any of the Examples 28 to 34, wherein said        transparent layer comprises a protective layer for said        eyepiece.    -   37. The system of any of the above Examples, further comprising:        -   at least one waveguide;        -   at least one coupling optical element configured such that            light from said output of said fiber that is reflected from            said eye is coupled into said waveguide and guided therein;            and        -   at least one out-coupling element configured to couple light            guided within said waveguide out of said waveguide and            direct said light to said at least one camera to capture            images of said eye.    -   38. The system of any of the Examples above, wherein said system        is configured to perform eye tracking based on images of said        eye captured by said camera.    -   39. The system of any of the Examples above, further comprising        a diffuser at said output of said elongate light guide at said        first end of said elongate light guide.    -   40. The system of any of the Examples above, wherein said angled        reflector is polished.    -   41. The system of any of the Examples above, wherein said at        least one light source comprises a UV or visible light source.    -   42. The system of any of the Examples above, wherein said at        least one elongate light guide has a length to thickness ratio        of at least 10.    -   43. The system of any of the Examples above, wherein said at        least one elongate light guide has a length to thickness ratio        of at least 20.    -   44. The system of any of the Examples above, wherein said at        least one elongate light guide comprises an optical fiber.    -   45. The system of any of the Examples above, wherein said at        least one elongate light guide comprises an optical rod        comprising optically transmissive material.    -   46. The system of any of the above Examples, wherein said at        least one elongate light guide comprises a plurality of optical        fibers.    -   47. The system of any of the above Examples, wherein said at        least one elongate light guide comprises a plurality of an        optical rods.    -   48. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   a transparent layer supported on said frame and disposed at            a location in front of the user's eye when the user wears            said head-mounted display such that said transparent layer            transmits light from an environment in front of the user to            the user's eye to provide a view of the environment in front            of the user, said transparent layer comprising front and            rear major surfaces surrounded by a plurality of edges, said            transparent layer further comprising and at least one tilted            surface, said tilted surface angled such that light guided            within said transparent layer is reflected from said tilted            surface and directed through said rear major surface out of            said transparent layer to said eye; and        -   at least one camera disposed to receive at least a portion            of the light reflected from the user's eye to capture images            using light reflected from the user's eye.    -   49. The system of any of the above Examples, wherein said tilted        surface comprises metallization.    -   50. The system of any of any of the above Examples, wherein said        tilted surface comprises IR reflective coating.    -   51. The system of any of the above Examples, wherein said tilted        surface is angled from 35° to 55° with respect to front and/or        rear major surface of said transparent layer.    -   52. The system of any of the above Examples, further comprising        at least one light source disposed with respect to said at least        one transparent layer such that light from said at least one        light source is injected into said at least one transparent        layer, is incident on said tilted surface, and reflected        therefrom toward the eye of the user.    -   53. The system of any of the above Examples, further comprising        at least one light source disposed with respect to at least one        edge of said transparent layer such that light from said at        least one light source is injected into said at least one        transparent layer, is incident on said tilted surface and        reflected therefrom toward said eye of said user.    -   54. The system of Examples 52 or 53, wherein said at least one        light source comprises a plurality of spaced apart light        sources.    -   55. The system of any of Examples 52 to 54, wherein said light        source comprises one or more infrared light sources.    -   56. The system of Examples 54 or 55, wherein said plurality of        light sources comprises three light sources.    -   57. The system of any of Examples 54 to 56, wherein said        plurality of light sources comprises four light sources.    -   58. The system of any of Examples 52 to 57, wherein said light        source creates a point source illuminating said eye of the user.    -   59. The system of any of Examples 54 to 58, wherein said        plurality of light sources creates a plurality of point sources        illuminating said eye of the user.    -   60. The system of any of the above Examples, wherein four light        sources create four point sources illuminating said eye of the        user.    -   61. The system of any of Examples 54 to 60, wherein said light        source comprises one or more light emitting diodes (LEDs) or        lasers.    -   62. The system of any of Examples 54 to 61, wherein said light        from said light source is guided within said transparent layer        by total internal reflection off said front and rear surfaces of        said transparent layer.    -   63. The system of any of the above Examples, wherein said        transparent layer comprises plastic.    -   64. The system of any of the above Examples, wherein said tilted        surface is planar.    -   65. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   66. The system of Example 65, wherein said eyepiece is        configured to receive light from said image projector and to        direct said light into said user's eye to display augmented        reality image content to the user's vision field.    -   67. The system of Examples 65 or 66, wherein said eyepiece        comprises at least one waveguide.    -   68. The system of Example 67, wherein said image projector is        configured to direct light into said at least one waveguide.    -   69. The system of Examples 67 or 68 above, wherein said at least        one waveguide comprises a stack of waveguides.    -   70. The system of Example 69, wherein different waveguides of        the stack of waveguides are configured to output light with        different wavefront divergence as if projected from different        distances from the user's eye.    -   71. The system of Example 69 or 70, wherein different waveguides        of the stack of waveguides are configured to output light with        different colors.    -   72. The system of any of the above Examples 65 to 71, wherein        said transparent layer comprises a layer in said eyepiece.    -   73. The system of any of the above Examples 65 to 71, wherein        said transparent layer comprises a protective layer for said        eyepiece.    -   74. The system of any of the above Examples, further comprising:        -   at least one waveguide;        -   at least one coupling optical element configured such that            light output from said transparent layer that is reflected            from said eye is coupled into said waveguide and guided            therein; and        -   at least one out-coupling element configured to couple light            guided within said waveguide out of said waveguide and            direct said light to said camera to capture images of said            eye.    -   75. The system of any of the Examples above, wherein said system        is configured to perform eye tracking based on images of said        eye captured by said camera.    -   76. The system of any of the Examples above, wherein said at        least one light source comprises a UV or visible light source.

Example Section IX

-   -   1. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   a camera;        -   at least one waveguide;        -   at least one coupling optical element configured such that            light is coupled into said waveguide and guided therein; and        -   first and second light redirecting elements disposed to            receive light from said at least one coupling optical            element that is guided within the waveguide,        -   wherein the first light redirecting element is configured to            direct at least a portion of the light received from said at            least one coupling optical element to the second light            redirecting element for outcoupling to said camera, and        -   wherein the second light redirecting element is configured            to direct at least of a portion of the light received from            said at least one coupling element to the first light            redirecting element for outcoupling to said camera.    -   2. The system of any of the Examples above, wherein said first        and second light redirecting elements form an angle with respect        to each other.    -   3. The system of any of the Examples above, wherein said first        and second light redirecting elements form an angle with respect        to each other of greater than 0° less and less than 180°.    -   4. The system of any of the Examples above, wherein said first        and second light redirecting elements form an angle with respect        to each other of greater than 75° less and less than 160°.    -   5. The system of any of the Examples above, wherein said first        and second light redirecting elements are angled with respect to        each other so as to form a chevron shape.    -   6. The system of any of the Examples above, wherein the first        and second light redirecting elements comprise diffractive        optical elements.    -   7. The system of any of the Examples above, wherein the first        and second light redirecting elements each comprise diffractive        features and the diffractive features of the first redirecting        element and the diffractive features of the second redirecting        element are oriented an angle with respect to each other.    -   8. The system of any of the Examples above, wherein the        diffractive features of the first redirecting element and the        diffractive features of the second redirecting element are        oriented an angle with respect to each other of more than 90°        and less than 170°.    -   9. The system of any of the Examples above, wherein the        diffractive features of the first redirecting element and the        diffractive features of the second redirecting element are        oriented an angle with respect to each other of more than 100°        and less than 140°.    -   10. The system of any of the Examples above, wherein first and        second redirecting elements have a straight border therebetween,        said first and second redirecting element configured to direct        light to said border.    -   11. The system of any of the Examples above, wherein first and        second redirecting elements have non-straight border        therebetween.    -   12. The system of any of the Examples above, wherein first and        second redirecting elements have an undulating border        therebetween.    -   13. The system of any of the Examples above, wherein first and        second redirecting elements have a sawtooth shaped border        therebetween.    -   14. The system of any of the Examples above, wherein first and        second redirecting elements are interlocking.    -   15. The system of any of the Examples above, wherein a region of        the first light redirecting element extends further away from        the center of the second light redirecting element and closer to        the center of the first light redirecting element than a portion        of the first light redirecting element.    -   16. The system of any of the Examples above, wherein a region of        the second light redirecting element extends further away from        the center of the second light redirecting element and closer to        the center of the first light redirecting element than a portion        of the first light redirecting element.    -   17. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled with respect to each other.    -   18. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled about 120° with respect to each other.    -   19. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled between 130° to 150° with respect to each        other.    -   20. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled between 140° to 160° with respect to each        other.    -   21. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled about 60° with respect to a centerline        between the first and second redirecting elements.    -   22. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled between 50° to 70° with respect to a        centerline between the first and second redirecting elements.    -   23. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector, said        grating vectors angled between 40° to 80° with respect to a        centerline between the first and second redirecting elements.    -   24. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector and        the at least one coupling optical element has a grating vector,        and the sum of these grating vectors is less than ½ degree.    -   25. The system of any of the Examples above, wherein the first        and second redirecting elements each have a grating vector and        the at least one coupling optical element has a grating vector,        and the sum of these grating vectors is zero.    -   26. The system of any of the Examples above, further comprising        at least one out-coupling element configured to couple light        from the at least one coupling element that is guided within        said light guide out of said light guide.    -   27. The system of any of the Examples above, wherein said at        least one out-coupling element is between said at least one        coupling optical element and said first and second light        redirecting elements.    -   28. The system of any of the Examples above, wherein at least        one out-coupling element is aligned along a centerline between        said first and second light redirecting elements.    -   29. The system of any of the Examples above, wherein at least        one out-coupling element is aligned along a gap between said        first and second light redirecting elements.    -   30. The system of any of the Examples above, further comprising        at least one out-coupling element configured to couple light        from the at least one coupling optical element that is guided        within said light guide out of said light guide that would        otherwise pass through a gap between the first and second light        redirecting elements.    -   31. The system of any of the Examples above, wherein one or more        of the first and second light redirecting optical elements and        the at least one coupling optical element comprise liquid        crystal gratings.    -   32. The system of any of the Examples above, wherein the first        and second light redirecting optical elements as well as the at        least one coupling optical element comprise liquid crystal        gratings.    -   33. The system of any of the Examples above, wherein said second        light redirecting element is configured to couple at least of        portion of the light from said first redirecting element out of        said waveguide to said camera.    -   34. The system of any of the Examples above, wherein said first        light redirecting element is configured to couple at least of        portion of the light from said second light redirecting element        out of said waveguide to said camera.    -   35. The system of any of the Examples above, wherein a        field-of-view produced by light collected by the at least one        coupling optical element that reaches the camera and contributes        to an image produced by the camera after being directed by the        first and second light redirecting elements to the coupling area        is larger than the field-of-view produced by light collected by        the at least one coupling optical element that reach the camera        and contributes to an image produced by the camera after being        directed to only one of the first or second light redirecting        elements to the coupling area.    -   36. The system of any of the Examples above, wherein said at        least one coupling optical element is configured such that light        reflected from the eye of the user wearing the head mounted        display system is coupled into said at least one waveguide and        guided therein such that images of said eye may be captured by        said camera.    -   37. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   38. The system of Example 37, wherein said eyepiece is        configured to receive light from said image projector and to        direct said light into said user's eye to display augmented        reality image content to the user's vision field.    -   39. The system of any of Examples 37-38, wherein said eyepiece        comprises said at least one waveguide.    -   40. The system of any of the Examples above, further comprising        at least one in-coupling optical element configured to in-couple        light from said image projector into said at least one waveguide        so as to guide light from said image projector for providing        said image content to said user's eye.    -   41. The system of any of the Examples above, wherein said at        least one coupling optical element is also configured to couple        light from said image projector guided within said waveguide out        of said at least one waveguide such that image content can be        viewed by the user's eye.    -   42. The system of any of the Examples above, wherein the same        coupling optical element is configured to couple light from said        image projector guided within said waveguide out of said        waveguide such that image content can be viewed by the user's        eye and to couple light into said at least one waveguide to be        guided therein to said camera.    -   43. The system of any of Examples 1 to 40, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said        waveguide out of said at least one waveguide such that image        content can be viewed by the user's eye.    -   44. The system of any of the Examples above, wherein said at        least one coupling optical element faces the eye of the user        wearing the head mounted imaging system to receive light from        said eye.    -   45. A head mounted display system configured to project light to        an eye of a user to display augmented reality image content in a        vision field of said user, said head-mounted display system        comprising:        -   a frame configured to be supported on a head of the user;        -   an image projector configured to project images into the            user's eye to display image content in the vision field of            the user;        -   a camera;        -   at least one waveguide;        -   a coupling optical element configured such that light is            coupled into said waveguide and guided therein; and        -   an out-coupling optical element disposed to receive light            from said coupling element that is guided within the            waveguide,        -   wherein the out-coupling optical element is configured to            out-couple light from said coupling optical element guided            within said waveguide out of said waveguide to said camera.    -   46. The system of any of the Examples above, wherein said        out-coupling optical element is disposed to receive light from        said coupling optical element that is guided within the        waveguide via an optical path that extends from the coupling        optical element to the out-coupling optical element without any        intervening light redirection optical elements or gratings.    -   47. The system of any of the Examples above, wherein the        coupling optical element and said out-coupling optical element        each have a grating vector, and the sum of these grating vectors        is less than ½ degree.    -   48. The system of any of the Examples above, wherein the        coupling optical element and said out-coupling optical element        each have a grating vector, and the sum of these grating vectors        is zero.    -   49. The system of any of the Examples above, wherein one or more        of the coupling element and the out-coupling optical element        comprise liquid crystal gratings.    -   50. The system of any of the Examples above, wherein the        coupling element and the out-coupling optical element comprise        liquid crystal gratings.    -   51. The system of any of the Examples above, wherein said        coupling optical element is configured such that light reflected        from the eye of the user wearing the head mounted display system        is coupled into said at least one waveguide and guided therein        such that images of said eye may be captured by said camera.    -   52. The system of any of the Examples above, further comprising        an eyepiece disposed on the frame, said eyepiece configured to        direct light into said user's eye to display augmented reality        image content to the user's vision field, at least a portion of        said eyepiece being transparent and disposed at a location in        front of the user's eye when the user wears said head-mounted        display such that said transparent portion transmits light from        an environment in front of the user to the user's eye to provide        a view of the environment in front of the user.    -   53. The system of Example 52, wherein said eyepiece is        configured to receive light from said image projector and to        direct said light into said user's eye to display augmented        reality image content to the user's vision field.    -   54. The system of any of Examples 52-53, wherein said eyepiece        comprises said at least one waveguide.    -   55. The system of any of the Examples above, further comprising        at least one in-coupling optical element configured to in-couple        light from said image projector into said at least one waveguide        so as to guide light from said image projector for providing        said image content to said user's eye.    -   56. The system of any of the Examples above, wherein said        coupling optical element is also configured to couple light from        said image projector guided within said waveguide out of said at        least one waveguide such that image content can be viewed by the        user's eye.    -   57. The system of any of the Examples above, wherein the same        coupling optical element is configured to couple light from said        image projector guided within said waveguide out of said        waveguide such that image content can be viewed by the user's        eye and to couple light into said at least one waveguide to be        guided therein to said camera.    -   58. The system of any of Examples 1 to 55, further comprising at        least one image content out-coupling optical element configured        to couple light from said image projector guided within said        waveguide out of said at least one waveguide such that image        content can be viewed by the user's eye.    -   59. The system of any of the Examples above, wherein said        coupling optical element faces the eye of the user wearing the        head mounted imaging system to receive light from said eye.    -   60. The system of any of Examples 1-44, wherein said first and        second light redirecting elements are disposed on opposite sides        of the waveguide.    -   61. The system of any of Examples 1-44, wherein said first light        redirecting element is disposed on the front side of the        waveguide and the second light redirecting element is disposed        on the back side of the waveguide or the second light        redirecting element is disposed on the front side of the        waveguide and the first light redirecting element is disposed on        the back side of the waveguide.    -   62. The system of any of Examples 60 or 61, wherein said first        and second light redirecting elements have regions that overlap        thereby.    -   63. The system of any of the examples above, wherein said        coupling optical element, said first light redirecting element,        said second light redirecting element, or any combination        thereof comprises a graded diffractive optical element.    -   64. The system of any of the examples above, wherein said        coupling optical element, said first light redirecting element,        said second light redirecting element, or any combination        thereof comprises a graded diffractive optical element having a        diffraction efficiency that is graded.    -   65. The system of any of the examples above, wherein said        coupling optical element, said first light redirecting element,        said second light redirecting element, or any combination        thereof comprises a graded diffractive optical element having a        diffraction efficiency that is graded to increase image        uniformity.    -   66. The system of any of the examples above, wherein said        coupling optical element, said first light redirecting element,        said second light redirecting element, or any combination        thereof comprises a graded diffractive optical element having        grating thickness or duty cycle that is graded.    -   67. The system of any of the examples above, wherein said        coupling optical element, said first light redirecting element,        said second light redirecting element, or any combination        thereof comprises a graded liquid crystal diffractive optical        element having grating thickness or helical pitch that is        graded.

Terminology

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense.

Indeed, it will be appreciated that the systems and methods of thedisclosure each have several innovative aspects, no single one of whichis solely responsible or required for the desirable attributes disclosedherein. The various features and processes described above may be usedindependently of one another, or may be combined in various ways. Allpossible combinations and subcombinations are intended to fall withinthe scope of this disclosure.

Certain features that are described in this specification in the contextof separate embodiments also may be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment also may be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially exampled as such, one or more featuresfrom an exampled combination may in some cases be excised from thecombination, and the exampled combination may be directed to asubcombination or variation of a subcombination. No single feature orgroup of features is necessary or indispensable to each and everyembodiment.

It will be appreciated that conditional language used herein, such as,among others, “can,” “could,” “might,” “may,” “e.g.,” and the like,unless specifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/or stepsare included or are to be performed in any particular embodiment. Theterms “comprising,” “including,” “having,” and the like are synonymousand are used inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list. Inaddition, the articles “a,” “an,” and “the” as used in this applicationand the appended examples are to be construed to mean “one or more” or“at least one” unless specified otherwise. Similarly, while operationsmay be depicted in the drawings in a particular order, it is to berecognized that such operations need not be performed in the particularorder shown or in sequential order, or that all illustrated operationsbe performed, to achieve desirable results. Further, the drawings mayschematically depict one more example processes in the form of aflowchart. However, other operations that are not depicted may beincorporated in the example methods and processes that are schematicallyillustrated. For example, one or more additional operations may beperformed before, after, simultaneously, or between any of theillustrated operations. Additionally, the operations may be rearrangedor reordered in other embodiments. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the embodiments describedabove should not be understood as requiring such separation in allembodiments, and it should be understood that the described programcomponents and systems may generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other embodiments are within the scope of the followingexamples. In some cases, the actions recited in the examples may beperformed in a different order and still achieve desirable results.

Accordingly, the disclosure are not intended to be limited to theembodiments shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

1. A head mounted display system configured to project light to an eyeof a user to display augmented reality image content in a vision fieldof said user, said head-mounted display system comprising: a frameconfigured to be supported on a head of the user; an image projectorconfigured to project images into the user's eye to display imagecontent in the vision field of the user; a camera; at least onewaveguide; at least one coupling optical element configured such thatlight is coupled into said waveguide and guided therein; and first andsecond light redirecting elements disposed to receive light from said atleast one coupling optical element that is guided within the waveguide,wherein the first light redirecting element is configured to direct atleast a portion of the light received from said at least one couplingoptical element to the second light redirecting element for outcouplingto said camera, and wherein the second light redirecting element isconfigured to direct at least of a portion of the light received fromsaid at least one coupling element to the first light redirectingelement for outcoupling to said camera.
 2. The system of claim 1,wherein said first and second light redirecting elements form an anglewith respect to each other.
 3. The system of claim 1, wherein said firstand second light redirecting elements form an angle with respect to eachother of greater than 0° less and less than 180°.
 4. The system of claim1, wherein said first and second light redirecting elements form anangle with respect to each other of greater than 75° less and less than160°.
 5. The system of claim 1, wherein said first and second lightredirecting elements are angled with respect to each other so as to forma chevron shape.
 6. The system of claim 1, wherein the first and secondlight redirecting elements comprise diffractive optical elements.
 7. Thesystem of claim 1, wherein the first and second light redirectingelements each comprise diffractive features and the diffractive featuresof the first redirecting element and the diffractive features of thesecond redirecting element are oriented an angle with respect to eachother.
 8. The system of claim 1, wherein the diffractive features of thefirst redirecting element and the diffractive features of the secondredirecting element are oriented an angle with respect to each other ofmore than 90° and less than 170°.
 9. The system of claim 1, wherein thediffractive features of the first redirecting element and thediffractive features of the second redirecting element are oriented anangle with respect to each other of more than 100° and less than 140°.10. The system of claim 1, wherein first and second redirecting elementshave a straight border therebetween, said first and second redirectingelement configured to direct light to said border.
 11. The system ofclaim 1, wherein first and second redirecting elements have non-straightborder therebetween.
 12. The system of claim 1, wherein first and secondredirecting elements have an undulating border therebetween.
 13. Thesystem of claim 1, wherein first and second redirecting elements have asawtooth shaped border therebetween.
 14. The system of claim 1, whereinfirst and second redirecting elements are interlocking.
 15. The systemof claim 1, wherein a region of the first light redirecting elementextends further away from the center of the second light redirectingelement and closer to the center of the first light redirecting elementthan a portion of the first light redirecting element.
 16. The system ofclaim 1, wherein a region of the second light redirecting elementextends further away from the center of the second light redirectingelement and closer to the center of the first light redirecting elementthan a portion of the first light redirecting element.
 17. The system ofclaim 1, wherein the first and second redirecting elements each have agrating vector, said grating vectors angled with respect to each other.18. The system of claim 1, wherein the first and second redirectingelements each have a grating vector, said grating vectors angled about120° with respect to each other.
 19. The system of claim 1, wherein thefirst and second redirecting elements each have a grating vector, saidgrating vectors angled between 130° to 150° with respect to each other.20. The system of claim 1, wherein the first and second redirectingelements each have a grating vector, said grating vectors angled between140° to 160° with respect to each other. 21.-67. (canceled)